What is the ruling on reading books that contain innovations (bid'ah) or fallacies, such as dedicating specific supplications (du'a) or prayers (salat) to certain days or months, like the month of Rajab and Ashura?

A Muslim must not expose himself to fitan (trials/temptations). Books of innovations and evil deeds can affect their reader. Therefore, the reader should seek what benefits them and abandon what harms them, contenting themselves with sound books such as "Riyad al-Salihin" and the Six Books. The discerning and knowledgeable critic is not prevented from reading these books in order to critique them and expose their deviation, but this is only permissible for a well-grounded scholar.