To Save a Thousand Souls, Fr. Brett Brannen
Truth in advertising (or reviewing): Fr. Brannen was my formation advisor in seminary. I learned an immense amount from him and count myself fortunate in being able to regard him as a friend. So this isn't necessarily the most unbiased of reviews.
That being said, I am still confident I'd give the book a good review even if I'd never met the author. His primary audience is the man who thinks he might have a vocation to the diocesan priesthood, but nearly anyone interested in how Catholic priests become priests, from the moment of the first hint of a call through the day of ordination, will learn much from this book.
I've been ordained nearly three years (it seems a short time and forever simultaneously), and I was going through the period of serious discernment nearly a decade ago. I wish this book had existed then, and I wish I'd had a copy. Some of what I found was simply confirmation that what I'd experienced was typical; some of it addressed the fears I had to work through in other ways; and some of it was simply advice that I eventually figured out on my own eventually, a process that would have been easier had someone been able to point it out to me at the time.
Advice about prayer? It's here.
Information about what to expect? It's here.
Warnings of pitfalls and how to avoid them? They're here, along with advice on how to get back up if you've fallen.
And all of it is straightforward, clear, and without pretense.
Buy a copy for yourself, and give one to someone you know who's discerning.