I don't know his printed work, but I guess I should get ahold of Book of Mercy. I'm a latecomer to the music -- read a ton of reviews of his stuff, going back 40 years, but resisted buying any of it. I was heartily sick of 'Suzanne', which was played endlessly by every amateur guitarist I knew in the early 70s -- the way you can get sick of Bridge Over Troubled Water or Kum Ba Ya. Every other folkie or female vocalist seemed to cover it, along with Bird on a Wire. Then Judy Collins covered Take This Longing, and it was such a pure performance with a sinuous, dreamy melody that I played it over and over. (She found more melody in the song than Cohen put into his original version.) Finally, in 2016, I bought Essential Leonard Cohen. It arrived at my house the very day that his obituary ran in the paper. Strange! I subsequently got a few of his live recordings, which I prefer to the Columbia studio cuts. His backup bands in concert give him just the right support, I think. If you listen to Essential it becomes stark and monotonous.
A few things I don't like -- Chelsea Hotel, which is about Janis Joplin, and comes off as petty and mean, as if he's settling accounts with her. In general, I find some of his lyrics to be overwritten -- to my taste, they have a graduate-student-journaling-in-Starbucks quality.
In the latter half of his career, he wrote and performed some sly, jaunty material that was missing in the early LPs. I particularly like I'm Your Man (everybody does; it was Roger Ebert's favorite song), Dance Me to the End of Love, Got a Little Secret, Everybody Knows. (Ands some of these may be from his early works, which I don't know cut for cut. If you're a Cohen expert, go ahead and correct my assumed chronology.)
Hallelujah is presumed to be his masterpiece. I'm not ravished by this track. It has a formal perfection, but I never feel drawn into the lyric. Maybe it will grow on me. His song about Joan of Arc is one of those Starbucks-infused lyrics, but I like it.
Cohen went a long way with a limited vocal range. I think the music will still be listened to fifty or a hundred years hence, the way all the extreme individualists in music make a claim on successive generations.
There's a wide chasm between the lyrics in his music and his poetry. I appreciate much of the music he's put out, but poetry is his art form (it just doesn't put bread on the table as readily as music does).
Book of Mercy is a wonderful book, but Book of Longing is definitely more accessible (although I'm certain you specifically will enjoy both). I've read a good chunk of Cohen's poetry, and I'll grant that some of his earlier work suffered from the usual pitfalls of writing while young. But the two aforementioned books written in the latter half of his life are masterpieces, and I'll be happy if I can find something else I enjoy half as much.
Book of Mercy was his kind of - grappling with existence, God, the divine, beyond the drama of day to day life, for a bit of a sneak peek check out some of the reviews on Goodreads, you may find yourself surprised. Oddly enough, he released Book of Longing after Book of Mercy, which was more of a standard collection, but as far as I can tell more went into it than any of his other works.
The one that was released just after his death, The Flame, gives the impression of an unfinished work that was rushed out to capitalize on the situation. Anyway.. definitely buy the two.