Oh dear, my mind went blank when I read this question. My favourite book - which one is that? And one that other people haven't heard of? I tend not to talk about books much to anyone these days apart from my family and people at the book groups I go to and talking to these people we usually find out about books the others haven't heard of. Reading blogs I come across so many books that I haven't heard of too, so maybe other people haven't heard of the ones I like.
Trying to think what is my favourite book I looked at my catalogue on LibraryThing. I liked The Poisonwood Bible - 6,578 other people own that book - so not unknown. How about Things Fall Apart? No, 3,805 others have that. So on and so forth.
I think I've mentioned Melvyn Bragg's book A Son of War before, but that is one book I liked that not many other people on LibraryThing own (41 others). The Man Who Listens by Taylor Caldwell is another - only one other person has that in their catalogue. How about Lambs of God by Marele Day (75 others have it) or Winter in the Hills by John Wain (10 others)? I liked these too, but I'm not sure they're my favourites.
There is poetry. No one that I've talked to has heard of Jack Mapanje or his books Of Chameleons and Gods (4 others on LT) and The Chattering Wagtails of Mikuyu Prison (1 other person). I don't read a lot of poetry, but I was really taken with these, maybe because I first heard them read by Jack when I was at a Summer School for an Open University course on English Literature. Jack was imprisoned in Malawi from September 1987 to May 1991, detained without charge or trial. Hearing him tell of his experiences was so moving.