I've reviewed a few books online for the MAA. When I learned undergraduate differential geometry with John Terrilla, we used O'Neill and Do Carmo and both are very good indeed. O'Neill is a bit more complete, but be warned - the use of differential forms can be a little unnerving to undergraduates. That being said, there's probably no gentler place to learn about them. I do think it's important to study a modern version of classical DG first (i.e. curves and surfaces in R3, emphazing vector space properties) before going anywhere near forms or manifolds - linear algebra should be automatic for any student learning differential geometry at any level.

If you are looking for text that is good for an undergraduate course in differential geometry, I would suggest Differential Geometry of Curves and Surfaces by Banchoff and Lovett. See -Geometry-Curves-Surfaces-Banchoff/dp/1568814569/ref=sr_1_3?ie=UTF8&qid=1317835776&sr=8-3 . It was published in 2010 so did not show up on this earlier.




Elementary Differential Geometry Barrett O'neill Pdf 17