For those with large libraries, the prospects of searching all ones books for some stray crumbs that may have gotten wedged within them is daunting.
The obligation to do a bedika or search for Chametz is only applicable to places where one is wont to use and bring Chametz. So books that were not used at the table and one didn’t use when eating definitely don’t have to be checked.
The Magen Avraham writes that crumbs don’t require specific nullification and only that which one may want to keep ( a “gluska yafeh”) requires bittul. According to this reasoning there should be no obligation to check ones seforim for crumbs either.
There are however other Poskim who dispute the assertion of the Magen Avraham and feel that one may end up eating the crumbs as well and therefore they do require bittul and bedikah. Additionally, there is a oft quoted Rosh that the Minhag of all Jews is to eradicate all Chametz from their possession, even that Chometz which one may not Halachically be required to remove from his custody. This is used often to explain customs like washing the ceilings and painting the outside of the house in advance of Pesach. It seems to be applicable here as well.
Furthermore, the Arizal says that if someone is careful about even the tiniest bit of Chametz they will be assured to be free of sin for the entire year. [I’m not sure how to understand things like this but maybe it’ll help someone else].
The best solution is for one to be careful throughout the year not to eat Chametz near their seforim and books and thus eliminate all doubt.