Scott Knaster’s Take Control of Switching to the Mac explains the Mac to someone who has known only Windows. PDF format, 93 pages, free 21-page excerpt available. Publication date: November 17, 2005. Price: US$10.
I haven’t read this one but the Take Control series is one I trust.
These days Macs and Windows are pretty similar — it’s mainly a matter of understanding the ‘translations’, such as the Close control for a window is at top left instead of top right. In fact I’ve noticed that Windows users generally have the most trouble when they try to make things too hard. I’m sure this book will be helpful.