I’m not sure whether this category is for a book written years ago that I read recently, or a book I read years ago that is still a favourite.
So, I've covered both options. In the former category I have to nominate Over Sea, Under Stone by Susan Cooper. Wonderful!
I discovered it as a result of discussions about covering the Dark is Rising sequence by Susan Cooper, of which this is the first in the sequence. How I missed these books as a child is beyond me, but so pleased to have read them now. Also, that I invested in the Folio editions, which are beautiful to look at and to read.
In the category of a favourite I read years ago, well there are so many, but I think it has to be The Chronicles of Narnia by C.S. Lewis. I loved these as a child, and re-read them recently. When I joined the Folio Socliety the joining offer included the Narnia books reduced from over £100 to £9.99 BARGAIN!