The Baja Almanac is the best thing for the Baja explorer,
http://www.baja-almanac.com/It contains a complete set of road maps overlaid on topographic (contour lines)maps. It is not the best as far as topos, but is far better than simple road maps.
Probably great for 98% of users. $25 + $3 shipping.
The National Geographic "Adventure Map" of Baja North #3103 and Baja South #3104 are great. Very detailed, colorful, shading, but no contour lines. It is GPS compatible, with UTM grid.
In addition to those, I have an out-of-print book containing complete detailed topos. If you are needing a topo for a specific area, perhaps I can help with that. Northern Baja wilderness is my playground. The forum on
http://www.bajanomad.com may also be of use.
My e-mail is ClimbBaja[at]aol{dot}com