I flipped through Three Pillars of Zen by Philip Kapleau Roshi. Seems like there are many good instructions on self-enquiry and self-realisation. Going to put it as a book recommendation in AtR guide.
(It's also highly recommended by
It’s an awesome book. Anyone reading should check out the “enlightenment stories” which are kensho stories written by people who have gone through it. Personal and varied. Also the “private encounter with ten westerners” it’s about dokusan. Rare recordings of what goes on in there.1
My favourite book on Zen by a mile. Indeed, for me, a rare case in which one book covers almost everything you'd need to know about a particular area of Buddhism
Guides to meditation (the one on the koan 'mu' helped me have a major En experience),
teacher exchanges with students
and wonderful stories of enlightenment (a rare thing: but its comforting that at least one tradition is evidence of the fact that a determined person can reach at least some of the enlightenments with a determined effort within a finite time).