What are the differences in meaning between these following sentences:

1. This is the same book that I read yesterday.

2. This is the same book as I read yesterday.


They are both a little odd. It is hard to see why anyone would say anything like that. It's "same" that causes the problem. You would just say "That is the book I read yesterday."

I think there is no difference in meaning between these two sentences.

You can use "the same ... that" or "the same ... as".