With such a wealth of titles available, and the field constatnly expanding, the obvious question is where to begin? To which the obvious reply is, where are you starting from?
The question matters. You need to be clear on whether you want a simple introduction, a general but comprehensive overview for playpeople, or a scholarly tome filled with notes, sources and all the necessary qualifications, ifs and buts. Are you looking for approaches rooted in Scripture, or Church teaching, or both? From a gay male, lesbian, or trans perspective? All these questions, and more, will influence your choice. In my detailed posts for each book, I have attempted to provide answers to these questions. The labels included in each post will help you to find books on a specific topic. With time, I will be building in thematic lists, a search engine, and other means to access exactly what you personally will find helpful - but all these refinements take time, while I am simultaneously trying to expand the number and range of books included. I crave your patience.
In the meantime, I offer some suggestions of what might be the most useful for specific purposes: