There are plenty available from various publications, you can do google search for the same.
but the best book is ISO 9001 - 2015 itself only.
Key to understanding
Its base on PDCA cycle - just understand it.
read the book from the start page and not from the required clause numbers.
a use of word 'shall' in any sentence in all clauses is indicative of the code need evidence of this thing happen correctly or monitored - means this documents need to be retained as a proof of work done. apart from this at some places direct references are made to keep records.
when you see a word 'should' written in any sentence - it only says we recommend it but if you don't it really does not matter because we are recommending and not enforcing.