a) He has already sent me the book he has read.
b) He has already sent me the book he read.
I am still struggling with the differences between present perfect and past simple. I have the amazing Oxford's book 'Practical English Usage' near me and even so I cannot make a decision between the sentences above.
The first part of the sentence(s) is clear:
He has already sent me... - I use the present perfect because the book was recently received by me.
The second part is the problem. It seems that I could use both:
a)...the book he has read - The book was read by him before, until now - because of that could I use the present perfect?
b)...the book he read - The book was read by him a long time ago, during the 90's decade - because of that could I use the past simple?
Shall I use either one or the other? or shall I use whatever tense I want?