That's also one of my main problems with Osprey's Men-at-Arms series ... but I guess it all depends what you're looking for. I actually haven't read too many of Osprey's books on the Civil War, but one that I did and can recommend is "
Confederate Artilleryman 1861-65" from the Warrior series. Years ago I participated in a Civil War reenactment as a CSA artilleryman, and reading that book was interesting because it gave a look not only at what the guys were wearing and carrying, but also things like their recruitment/training and the conditions of their daily life on campaign. When it comes to Osprey books I much prefer the Warrior series over Men-at-Arms for this reason, because Warrior books cover both equipment and service history, as opposed to just uniform details.