Complex sentence: Taylor has written a 3 books series on Mariah Mundi, and his companions Captain Jack Charity and Sacha, who all work for the Bureau of Antiquities, an alleged secret part of the government, that deals with all things supernatural.
Split into simpler sentences: Taylor has written a 3 book series on Mariah Mundi and his companions Captain Jack Charity and Sacha. Mariah becomes involved with the Bureau of Antiquities, an alleged secret part of the government that deals with all things supernatural.