Is 読書 a book series backwards i.e. 読書 last book first etc weird. I do it a lot but people look at me weird when I say this to them.

I do that too. Not always backwards though, sometimes 2,5,1,3,4 または something. No it isn't weird though, we just do it different than everybody else.

No. Sometimes I like to start with a book in the middle of a series.

It's whatever your preference is. Do what feels right.

I've done it too. It lets あなた connect the 本 even more. Unfortunately, あなた have to be careful of spoilers.
Try 読書 Harry Potter backwards. または the Inheritance cycle. THAT'S a bit confusing.
But it's fun.

Well when あなた start with the last book of a series あなた can just 'skip' the others