I read the book The Refugees and I got confused about Mankar's race.

Mankar was the illegitimate son of Camoran Usurper, a Bosmer, and his Bosmeri mistress, as it described in the book. So how would he become an Altmer? Did I misunderstand anything about the book or the lore?

One of the most important things you need to realize about the Elder Scrolls games, in terms of lore, is that everything you read or hear in a game is not necessarily true. The Elder Scrolls is full of http://en.wikipedia.org/wiki/Unreliable_narrator This is, for many of us, one of the things that makes this series so fascinating.

There is no direct evidence, other than the name, that Mankar Camoran is the illegitimate son of the Camoran Usurper. In fact, we can assume they are not, because of the race issue you mentioned. My own guess is that the names are a coincidence, like two people being named John Smith.

i think he was supposed to be a bosmer personally. however a four foot tall villain is hard to take serious. Also posting in the lore forum will probably help a lot more, they're into that weird metaphysics stuff that would explain his apperance (actually Mankar is a pretty interesting guy, being a possible dragonborn and such)