The only problem with your claim, and it's just a tiny, little one, is that you're completely wrong. I've done some actual research into this matter instead of blindly complaining about the same misconception other people do, and the results came up as about 90 books being written for Daggerfall, about 230 being written for Morrowind, and about 140 being written for Oblivion. Oblivion added plenty and the only way 80% of Oblivion's books could have been copied and pasted directly from the books created for Morrowind would have been if Morrowind had 560 books created for it and all of them were copy-pasted to Oblivion. Neither of those requirements are even close to true.
Books created for Oblivion:
Spoiler
1. http://www.uesp.net/wiki/Lore:A_Life_of_Uriel_Septim_VII
2. http://www.uesp.net/wiki/Lore:Rislav_The_Righteous
3. http://www.uesp.net/wiki/Lore:Ahzirr_Traajijazeri
4. http://www.uesp.net/wiki/Lore:History_of_the_Fighters_Guild
5. http://www.uesp.net/wiki/Lore:Fire_and_Darkness
6. http://www.uesp.net/wiki/Lore:The_Five_Tenets
7. http://www.uesp.net/wiki/Lore:Followers_of_the_Gray_Fox
8. http://www.uesp.net/wiki/Lore:Hiding_With_the_Shadow
9. http://www.uesp.net/wiki/Lore:Manifesto_Cyrodiil_Vampyrum
10. http://www.uesp.net/wiki/Lore:Necromancer%27s_Moon
11. http://www.uesp.net/wiki/Lore:Pension_of_the_Ancestor_Moth
12. http://www.uesp.net/wiki/Lore:Beggar
13. http://www.uesp.net/wiki/Lore:Thief
14. http://www.uesp.net/wiki/Lore:Warrior
15. http://www.uesp.net/wiki/Lore:King
16. http://www.uesp.net/wiki/Lore:The_Argonian_Account,_Book_1
17. http://www.uesp.net/wiki/Lore:The_Argonian_Account,_Book_2
18. http://www.uesp.net/wiki/Lore:The_Argonian_Account,_Book_3
19. http://www.uesp.net/wiki/Lore:The_Argonian_Account,_Book_4
20. http://www.uesp.net/wiki/Lore:Beggar_Prince
21. http://www.uesp.net/wiki/Lore:The_Exodus
22. http://www.uesp.net/wiki/Lore:Knightfall
23. http://www.uesp.net/wiki/Lore:Purloined_Shadows
24. http://www.uesp.net/wiki/Lore:The_Refugees
25. http://www.uesp.net/wiki/Lore:Thief_of_Virtue
26. http://www.uesp.net/wiki/Lore:The_Adabal-a
27. http://www.uesp.net/wiki/Lore:The_Amulet_of_Kings
28. http://www.uesp.net/wiki/Lore:Battle_of_Sancre_Tor
29. http://www.uesp.net/wiki/Lore:Before_the_Ages_of_Man
30. http://www.uesp.net/wiki/Lore:Cleansing_of_the_Fane
31. http://www.uesp.net/wiki/Lore:Daughter_of_the_Niben
32. http://www.uesp.net/wiki/Lore:Dwemer_History_and_Culture
33. http://www.uesp.net/wiki/Lore:Fall_of_Vitharn
34. http://www.uesp.net/wiki/Lore:The_Last_King_of_the_Ayleids
35. http://www.uesp.net/wiki/Lore:The_Legendary_Sancre_Tor
36. http://www.uesp.net/wiki/Lore:Lost_Histories_of_Tamriel
37. http://www.uesp.net/wiki/Lore:Remanada
38. http://www.uesp.net/wiki/Lore:The_Song_of_Pelinal,_v_1
39. http://www.uesp.net/wiki/Lore:The_Song_of_Pelinal,_v_2
40. http://www.uesp.net/wiki/Lore:The_Song_of_Pelinal,_v_3
41. http://www.uesp.net/wiki/Lore:The_Song_of_Pelinal,_v_4
42. http://www.uesp.net/wiki/Lore:The_Song_of_Pelinal,_v_5
43. http://www.uesp.net/wiki/Lore:The_Song_of_Pelinal,_v_6
44. http://www.uesp.net/wiki/Lore:The_Song_of_Pelinal,_v_7
45. http://www.uesp.net/wiki/Lore:Treatise_on_Ayleidic_Cities
46. http://www.uesp.net/wiki/Lore:Advances_in_Lock_Picking
47. http://www.uesp.net/wiki/Lore:Ayleid_Reference_Text
48. http://www.uesp.net/wiki/Lore:Bark_and_Sap
49. http://www.uesp.net/wiki/Lore:Calcinator_Treatise
50. http://www.uesp.net/wiki/Lore:De_Rerum_Dirennis
51. http://www.uesp.net/wiki/Lore:An_Elytra%27s_Life
52. http://www.uesp.net/wiki/Lore:From_Frog_to_Man
53. http://www.uesp.net/wiki/Lore:Fundaments_of_Alchemy
54. http://www.uesp.net/wiki/Lore:Heavy_Armor_Repair
55. http://www.uesp.net/wiki/Lore:History_of_Lock_Picking
56. http://www.uesp.net/wiki/Lore:Immortal_Blood
57. http://www.uesp.net/wiki/Lore:Light_Armor_Repair
58. http://www.uesp.net/wiki/Lore:Liminal_Bridges
59. http://www.uesp.net/wiki/Lore:Lithnilian%27s_Research_Notes
60. http://www.uesp.net/wiki/Lore:The_Liturgy_of_Affliction
61. http://www.uesp.net/wiki/Lore:The_Living_Woods
62. http://www.uesp.net/wiki/Lore:Mace_Etiquette
63. http://www.uesp.net/wiki/Lore:Magic_from_the_Sky
64. http://www.uesp.net/wiki/Lore:Manual_of_Armor
65. http://www.uesp.net/wiki/Lore:Manual_of_Arms
66. http://www.uesp.net/wiki/Lore:Manual_of_Spellcraft
67. http://www.uesp.net/wiki/Lore:Manual_of_Xedilian
68. http://www.uesp.net/wiki/Lore:The_Predecessors
69. http://www.uesp.net/wiki/Lore:Proper_Lock_Design
70. http://www.uesp.net/wiki/Lore:Reality_%26_Other_Falsehoods
71. http://www.uesp.net/wiki/Lore:Saints_and_Seducers
72. http://www.uesp.net/wiki/Lore:The_Shivering_Apothecary
73. http://www.uesp.net/wiki/Lore:The_Shivering_Bestiary
74. http://www.uesp.net/wiki/Lore:Souls,_Black_and_White
75. http://www.uesp.net/wiki/Lore:The_Standing_Stones
76. http://www.uesp.net/wiki/Lore:Varieties_of_Daedra
77. http://www.uesp.net/wiki/Lore:Way_of_the_Exposed_Palm
78. http://www.uesp.net/wiki/Lore:Agnar%27s_Journal
79. http://www.uesp.net/wiki/Lore:Amantius_Allectus%27_Diary
80. http://www.uesp.net/wiki/Lore:Ancotar%27s_Journal
81. http://www.uesp.net/wiki/Lore:A_Bloody_Journal
82. http://www.uesp.net/wiki/Lore:Brenus_Astis%27_Journal
83. http://www.uesp.net/wiki/Lore:Cap%27n_Dugal%27s_Journal
84. http://www.uesp.net/wiki/Lore:Cindanwe%27s_Notebook
85. http://www.uesp.net/wiki/Lore:Dar-Ma%27s_Diary
86. http://www.uesp.net/wiki/Lore:Diary_of_Springheel_Jak
87. http://www.uesp.net/wiki/Lore:The_Doors_of_Oblivion
88. http://www.uesp.net/wiki/Lore:Drothan%27s_Field_Journal
89. http://www.uesp.net/wiki/Lore:Drothan%27s_Journal
90. http://www.uesp.net/wiki/Lore:Father_of_the_Niben
91. http://www.uesp.net/wiki/Lore:Frostcrag_Spire_Memoirs
92. http://www.uesp.net/wiki/Lore:Gelebourne%27s_Journal
93. http://www.uesp.net/wiki/Lore:Greywyn%27s_Journal
94. http://www.uesp.net/wiki/Lore:Grommok%27s_Journal
95. http://www.uesp.net/wiki/Lore:Journal_of_the_Lord_Lovidicus
96. http://www.uesp.net/wiki/Lore:Log_of_the_Emma_May
97. http://www.uesp.net/wiki/Lore:The_Path_of_Transcendence
98. http://www.uesp.net/wiki/Lore:Ramblings_of_Audens_Avidius
99. http://www.uesp.net/wiki/Lore:The_Red_Kitchen_Reader
100. http://www.uesp.net/wiki/Lore:Sacred_Witness
101. http://www.uesp.net/wiki/Lore:Sir_Amiel%27s_Journal
102. http://www.uesp.net/wiki/Lore:Traelius%27_Journal
103. http://www.uesp.net/wiki/Lore:Traitor%27s_Diary
104. http://www.uesp.net/wiki/Lore:Macabre_Manifest
105. http://www.uesp.net/wiki/Lore:Report:_Disaster_at_Ionith
106. http://www.uesp.net/wiki/Lore:The_Warp_in_the_West_(book)
107. http://www.uesp.net/wiki/Lore:Mysterium_Xarxes
108. http://www.uesp.net/wiki/Lore:Tome_of_Unlife
109. http://www.uesp.net/wiki/Lore:Legend_of_Krately_House
110. http://www.uesp.net/wiki/Lore:Mannimarco,_King_of_Worms
111. http://www.uesp.net/wiki/Lore:The_Ravings_of_Fenroy
112. http://www.uesp.net/wiki/Lore:Song_of_Hrormir
113. http://www.uesp.net/wiki/Lore:The_Black_Arts_On_Trial
114. http://www.uesp.net/wiki/Lore:Myth_or_Menace%3F
115. http://www.uesp.net/wiki/Lore:16_Accords_of_Madness,_v._VI
116. http://www.uesp.net/wiki/Lore:16_Accords_of_Madness,_v._IX
117. http://www.uesp.net/wiki/Lore:16_Accords_of_Madness,_v._XII
118. http://www.uesp.net/wiki/Lore:Bible_of_the_Deep_Ones
119. http://www.uesp.net/wiki/Lore:The_Blessings_of_Sheogorath
120. http://www.uesp.net/wiki/Lore:Divining_the_Elder_Scolls
121. http://www.uesp.net/wiki/Lore:Heretical_Thoughts
122. http://www.uesp.net/wiki/Lore:Modern_Heretics
123. http://www.uesp.net/wiki/Lore:Mythic_Dawn_Commentaries_1
124. http://www.uesp.net/wiki/Lore:Mythic_Dawn_Commentaries_2
125. http://www.uesp.net/wiki/Lore:Mythic_Dawn_Commentaries_3
126. http://www.uesp.net/wiki/Lore:Mythic_Dawn_Commentaries_4
127. http://www.uesp.net/wiki/Lore:Myths_of_Sheogorath
128. http://www.uesp.net/wiki/Lore:Opusculus_Lamae_Bal_ta_Mezzamortie
129. http://www.uesp.net/wiki/Lore:The_Prophet_Arden-Sul
130. http://www.uesp.net/wiki/Lore:Shezarr_and_the_Divines
131. http://www.uesp.net/wiki/Lore:Ten_Commands:_Nine_Divines
132. http://www.uesp.net/wiki/Lore:Trials_of_St._Alessia
133. http://www.uesp.net/wiki/Lore:Glories_and_Laments
134. http://www.uesp.net/wiki/Lore:Guide_to_Anvil
135. http://www.uesp.net/wiki/Lore:Guide_to_Bravil
136. http://www.uesp.net/wiki/Lore:Guide_to_Bruma
137. http://www.uesp.net/wiki/Lore:Guide_to_Cheydinhal
138. http://www.uesp.net/wiki/Lore:Guide_to_Chorrol
139. http://www.uesp.net/wiki/Lore:Guide_to_the_Imperial_City
140. http://www.uesp.net/wiki/Lore:Guide_to_Leyawiin
141. http://www.uesp.net/wiki/Lore:Guide_to_New_Sheoth
142. http://www.uesp.net/wiki/Lore:Guide_to_Skingrad
I agree with your general point that Oblivion offered its share of new books.
I dont think however its fair to include in your list DLC specific books, or short lists, or atrocities like 'manual of armor', something that belongs in an actual paper manual and includes unforgettables like : 'Blacksmiths can forge heavy armor from iron, steel, dwarven, orchish [sic], ebony or daedric.' Argh.
Also many an Oblivion book was rare because only attainable through rare loot, like Daggerfall.
The copy/ pasted bookcases everywhere with the same lackluster books in them, the lack of new books that were nothing more than short lists or gameplay hints, together with the rarity of actual new lore or history or 'flavour' books..
Overall this made the game seem less 'booked.'