The U.S. Constitution provides basis for patent law which is set forth as the 35th title of the United States Code or '35 U.S.C'. However, that merely sets forth the foundation and the real nitty-gritty is set forth as title 37 of the Code of Federal Regulations or '37 C.F.R.'. These are the patent statutes and with a little help from the USPTO's Manual of Patent Examining Procedure (MPEP) guide and regulate nearly all transactions and maneuvers related to patents. Thus, nearly the entire body of patent law – is found in these three texts.
It is fairly difficult to read with understanding a text like the United States Code. However, there is plenty written about all of the major patent rules. Indeed, mountains of texts on each of these patent rules will easily be found via any well thought out Google session. There is really little need to actually refer to and/or read the code as it is written. A best understanding can be had by considering the detailed works presented by sophisticated authors on the various topics. Accordingly, the United States Code which forms all basis for patent law – won't help much at all in your understanding of the patent system.
Similarly for the Code of Federal Regulations, the text is a bit terse and a good understanding is more typically found in writings about various topics rather than in the rules themselves. However, title 37 which is directed to patents and trademarks is more detailed and parsable than the United States Code from which it depends. One can often refer to 37 CFR to learn of the precise nature of rules which pertain to patent prosecution and practice.
The MPEP is another matter entirely. It sets forth every detail of every step of the way. It is quite boring and lengthy. However, every possible transaction related to patent examination is likely to be found in this massive tomb. I'd like to see the faces of patent examiners on their first sighting of the book when their boss tells them this is their new bible. Inventors will find little joy trying to understand all the strange phrases found in a typical Office Action (patent examination report), however with reference to the MPEP and a generous portion of patience, one can decode the meaning of a patent examination. Therefore, the MPEP might be of some use to those who seek an understanding beyond that which their patent attorney provides. Best of luck.