What are the permissible, non-forbidden books that are allowed to be authored and sold? Is it permissible to write about non-Muslim scholars or modern devices? Is transferring information from the Internet without permission considered intellectual theft?

There is no sin in authoring works in permissible fields. The default is permissibility, except for what the Sharia has forbidden, such as books of disbelief, magic, astrology, and books that incite sins and indecencies. It is permissible to speak about non-Muslim scholars and inventors regarding what they have excelled in, without making them role models for Muslims. It is permissible to quote and benefit from sources, provided that the نقل الكلام [quoted material] is attributed to its owner and source.