In my opinion the best is:
Title: .Net for Visual FoxPro Developers
Author: Kevin McNeish (Edited by Cathi Gero)
Publisher: Hentzenwerke Publishing
There is also:
Title: Visual FoxPro to Visual Basic .NET
Author: Les Pinter
Publisher: Sams Publishing
I've actually made more headway through the Hentzenwerke book than the Sams but this could be because the style appeals better to my way of thinking. The Sams book focuses only on Visual Basic .Net; the Hentzenwerke book covers both Visual Basic .Net and C#.
Hope this helps,
Ben Sugden
"Remember to enjoy hunting - and that means relishing the search for the product that has never been advertised or placed handily at the front of the shop; Life begins on the uppermost shelf, avoid guide books and top 10's like the plague." - Ramsey Dukes