Along with studying the tafsir of the Quran, one should also make sure to study the sciences of the Quran (Uloom Al-Quran). Why? So that you get a complete overview of the history of the Quran, its compilation, the reason for revelation of various ayaat (verses), etc.
In English, we have very few in-depth works on this topic. One of them is this one: The Introduction to the Sciences of the Quran by Yasir Qadhi.
The quality of the scanning isn’t the best but for those who don’t have the hard copy, it’ll do. I’d advise the serious students of knowledge to go ahead and buy the book. It’s well worth it.