According to several Aĥaronim, one is required to search all of his books, page by page, because a crumb of ĥametz might have fallen into one of them. These authorities maintain that the objective of bedikat ĥametz is to remove every crumb of ĥametz from one’s possession, and this was the practice of Ĥazon Ish: he would check page by page the books he planned to read on Pesaĥ and then sell the rest of his books to a gentile and put a partition in front of them. In this manner, he exempted himself from the obligation to search them all.
However, according to those poskim who maintain that the purpose of bedikat ĥametz is to find pieces of ĥametz the size of a kezayit, clearly there is no need for such a thorough search of books, for it is inconceivable that there could be a kezayit of ĥametz between the pages of a book. In fact, even some of the stringent poskim who say that all ĥametz must be sought out maintain that one is not required to search for the sort of tiny crumbs one is liable to find in books, because even if one sees them on Pesaĥ, there is little concern that one will want to eat them.
Therefore, one should not search his books page by page, because this is overly stringent behavior and is even liable to result in a waste of Torah-study time. Indeed, the accepted practice is not to be stringent in this regard.
Nevertheless, one should not put books on the dining table during Pesaĥ unless he was careful to distance them from ĥametz throughout the year. Such books might contain a crumb of ĥametz, which could fall into some food on Pesaĥ, and any amount of ĥametz on Pesaĥ is forbidden, even if it is mixed with a much greater quantity of other foodstuffs. It is permissible, though, to read such books on a table at which one does not eat.
If during the year one places such books on the dining table between meals, he must be careful to clean the table well after eating, so that not a single crumb remains. Even the stringent poskim maintain that one who is careful all year long to distance his books from ĥametz, and when bringing them to the dining table is careful that no crumbs of ĥametz fall into them, is not required to search his books, because they are already considered ĥametz-free.
The status of the bookcase itself depends upon the household. If there are no children, and the adults are careful not to put any food on the bookshelves, no search is required. If there are children in the house who may have placed food there, one is required to search among the books and behind them. If the bookshelf was cleaned well beforehand, a casual search is sufficient.
. The opinion of Ĥazon Ish appears in Ĥazon Ish OĤ 116:18. Bedikat Ĥametz U-vi’uro 2:1 is very strict about small crumbs, but regarding the issue of checking books, states in 3:24 that the custom is not to be strict like Ĥazon Ish, since the crumbs in books are extremely small and insignificant. Responsa Or Le-Tziyon 1:32 disagrees with Ĥazon Ish and proves from Rambam that one need not be concerned with ĥametz that is smaller than a kezayit. However, as noted in the previous section, whenever there is a concern that a small crumb might mix into food, one must be stringent, and as such, one should not bring books that may have crumbs in them into contact with food on Pesaĥ.