Is it permissible to download copyrighted books from the internet to ascertain their suitability before purchasing them from a library that sells them at a low price, and then resorting to commissioning someone to buy them from distant areas if they are not available locally?

The basic principle is to act upon what the soul finds reassuringly correct from the sayings of scholars when they differ. It is permissible for someone afflicted with obsessive doubts (waswas) to adopt the easier opinion to avoid hardship. If the obsessive doubt regarding downloading books causes hardship, then it is permissible to adopt the easier opinion; otherwise, the original principle is to act upon what the soul finds reassuring. As for downloading a book to browse before purchasing, there is no harm in it if it is permitted; otherwise, it is not permissible, and one can browse in libraries.