Best one will cost you about $150+. It is called Sherman by RP Hunnicutt, long out of print and considered the "Bible" for Sherman enthusiasts.
For us ordinary humans, there are several decent ones. My favorite is called M4 Sherman by George Forty. He also does one called US Tanks of WW2 which covers the various tanks we used.
For model building, there is the MMiR Modelers Guide to the Sherman by Ampersand Publishing. Another OOP book that is well worth the search and covers the various Sherman kits in various scales, although 1/35 is its main focus.
Osprey Modelling Manuals 14 M4 Sherman is another decent volume that is still easily found.
Squadron Signal also does the M4 Sherman in Action and an excellent M4 Sherman Walkaround that is well worth the price ($8 and $14 respecitvely).