Nowadays there are plenty of different proofs of the celebrated Szemerédi's Theorem but for historical reasons I would like to read and understand the original proof. The proof is very tricky and, for instance, he uses a primitive version of the Regularity Lemma (weaker and more complicated), so I would like to find some source with a 'modern' language.

My question is then the following: is there any survey/book/... where the original proof is presented (with more details possibly), apart of course of the original paper?