Are there any original sources documenting the simplification process?
Simplified Chinese is no stupid command from "communist overlords". There was a committee discussing simplification, and they did choose simplified characters with academic discretion. I have found this semi-official book for explaining the sources of almost each simplified characters, plus the history of Chinese character simplification from Qing Dynasty:
《简化字溯源》(Tracing the Source of Simplified Characters), published by Language &amp; Culture Press, 1997. (It's not an English book, but this is all I can think of. )
You can borrow it from a library, or buy it online for about $6.
Edit:
For those who think Simplified Chinese is a brutal command from the "red evils":
Chinese simplification is a process that started thousands of years ago, which has been performed by various regimes, not just the Communist China.
Lishu(lit. "slave script") is the best-known simplification in Ancient China, promoted by Qin Shihuang. Before that, Xiaozhuan(lit. "minor seal (script)"), which is more complex with round and delicate curves, served as the official script (after Qin unified China).
In 1935, the KMT government had drafted a proposal of simplifying Chinese, which contains about 500 characters as the "first batch". Most of them were accepted by the current Simplified Chinese. It was rejected because Dai Li, the head of intelligence, strongly opposed the proposal with the reason "Simplified Chinese is abomination to the ancestors".
The current Simplified Chinese was sometimes called Yi-Jian ("First Simplification"), because there were Er-Jian ("Second Simplification") during the early 1980s, which was really a disaster. The Second Simplification was made in a hurry, with a lot of simplifications that may cause confusion, violate the principle of making Chinese characters, or be just too ugly. People around China also invented their own simplification arbitrarily, which brought more confusion. The Second Simplification was terminated in mid-1980s, and the standard Chinese script was rolled back to the First Simplification.
What I'd like to say is, Simplified Chinese we use today may be imperfect, but they're so widely used and tested in daily life, and it is the best existing solution besides Traditional Chinese, with less complexity, and introduces minimum confusion. It can be left today because it is based on extensive research and respect to the principles.