book comes from castles and olympiad
apart from the first book you get for finishing third class most ppl can expect never to get another one without paying for it
kinda sucks that you get to enchant skills then realize you basically have no way to get the books until nobless (or if you have a castle)
then if you actually get a book you realize it doesnt make sense to actually enchant until 78+
you can still enchant some skills though
the first thing a summoner does at 76 is +1 their summon which gives a pretty good boost for pretty good odds (80% successs i failed 3 times :/)