[6] The subject matter of theological novels often overlaps with philosophical novels, particularly when it deals with issues from natural theology (also called philosophy of religion).
For example, Roger Olson notes that the problem of evil is a feature of some significant theological fiction.
[7] Theological fiction also overlaps with religious fiction or Christian novels (also called inspirational fiction), especially when dealing with complex ideas such as redemption, salvation and predestination, which have a direct bearing on attitudes towards religious practices.
[8] Some authors try to distinguish a theological novel as one which denotes a more idea driven plot, rather than a novel which is about people who happen to be interacting with religion,[9] but the distinction often proves difficult to sustain when ideas and actions are closely interwoven, each influencing the other.
[11] Examples of linked series of theological fiction include: