I saw lot of comment on this, some said evo 180, some said exchange the books. What I did was lvl up 1 heroes to 200 and keep all the books for next hero that reach 180. the books is enough for other heroes up it lvl from 180 to 200. Does this approach good or better to exchange it for hb?
The only reason to take a hero to 200 is if you need the books.
The exp to book ratio is 1:1, so the only way to gain a benefit is with an enlightenment talent, or if you want to sell the books for HB.
If you are neither, there is no reason to wait.