Good literal translation is probably:
"It is- good- with me- the book"
The book is good with me
I like the book
Yes indeed. The most literal translation is in fact:
The book is a thing I consider good.
In this case "maith" is understood as an noun meaning "a good thing" and "maith liom" being "a thing I consider good".
So you can see this is just like other copular sentences:
Is maith liom é = He is a thing I consider good.
Is buachaill é = He is a boy.