Most if not all of the formulae are in imperial units though.
I consider that a cardinal sin in this day and age -
especially where electromagnetics are involved. Shame, I've seen the man talk and he clearly knows his stuff but the idea of having to wade through maxwells et al. puts me right off.
Some of my recommendations for basic digital design textbooks:
Digital Design by M. Morris Mano - a bit outdated but a good guide to fundamentals
Digital Design and Computer Architecture by David & Sarah Harris - covers the digital fundamentals and goes on to use them for basic computer design. If your tendencies are in this direction then this books is the starting point for you.
Digital Design - Principles and Practices - John F Wakerly - Most modern of the list. Again, sound basics but perhaps better treatment of recent trends such as programmable logic (CPLDs, FPGAs).
If people are looking for specific areas I've probably got quite a few recommendations for quite a few areas. My book collection is faitly heavy on digital topics, some quite specialized.