Bill, I agree with the books that Dave suggested. Here is another that is a verry good sourse for info ( here you will not find the depth of coverage on the specific Guns ( "Bess" & "Baker") but you will find a wealth of info on the guns leading up to them & those contempery to them),
"English Guns & Rifles" by J.N.George Note this book is out of print, but avail.
BTW- I own,shoot, been involved in building,etc "Bakers" they are a very interesting firearm.
Puffer