I'm an electrical engineer with the usual math background for engineering (mostly calculus, vector calculus, some DEs, Fourier, some complex analysis, linear algebra). Years ago I picked up a copy of Hungerford's Abstract Algebra: An Introduction (probably off of the streets of Cambridge MA when somebody cleaned out their apartment). I had absolutely no background in abstract algebra, but I've been able to teach myself from this book. It's slow going, but once in a while I'll pick it up and spend a few minutes reading before bed every night for a month before putting it back down. It's really interesting stuff and I've learned a ton.
My question: are there books on other topics (not abstract algebra) at a similar difficulty level? Something that a non-mathematician could use for self-learning? Most serious math books seem to jump right in with definitions and proofs. Hungerford motivates and explains a lot in plain English.
So...any ideas? Thanks in advance.