I've used clubbells and maces very extensively over quite a few years.
I have clubbells from 15 to 45lbs. I mostly used the 15s when I first started, and now 20s and 25s are my working weights for most one handed exercises (singles and doubles), and 35 and 45lbs for two handed exercises.
I also have a couple of plate loadable maces that I usually keep loaded with 22.5 to 25lbs.
I love the clubbells and maces because they work in planes/ranges/joint positions that KBs and barbells don't, they're great for anti-rotation, reflexive stability and conscious rooting and bracing, the ballistic nature of many of the drills is very easy on the joints, and they work the grip differently than almost any other implement.
To expand on the last two points. A lot of the ballistic CB exercises are less about generating maximum power or muscling throught the range of motion and more about managing and directing the momentum of the weight, as well as bracing and stabilizing against that momentum. The patterns of tension and relaxation are different from other implements and generally relatively low stress. For instance, after severely tearing my rotator cuff playing basketball, and then during my rehab after surgery, I was still able to do a lot of the ballistic club swinging pain free, which was NOT the case for the traditional Indian club drills with light 1 and 2lb clubs.
When you first start, however, be prepared for some crazy DOMS in your armpit area and the proximal area of the triceps. There are also some aspects of technique that are important to get right to avoid irritating the elbows.
I also find it easy to recover from even very large volumes of clubbell and mace ballistics. 32 repeats of 10 reps, on the minute (or 50 seconds) is a minimal volume that I'll throw on top of other training or do by itself on a recovery day. On weekends, I'll often do 100-200 reps of A+A style KB ballistics (sometimes a lot more, but most of my recent training is in that range), then do 400-600 total reps of CB and/or mace ballistics. A+A style works great for this. It's easy to fry your grip/forearms if you push sets too long. Keeping sets short allows me to do a lot of repeats and total volume and still recover well.
For the grip, CBs work the grip by pulling THROUGH your grip (like a vertical bar deadlift). It's sort of crushing grip, but not the same; it definitely has it's own feel. The grip also works very dynamically. There are patterns of tension and relaxation, and patterns of gripping harder and looser with different combinations of fingers, at different stages of each exercise.
Besides the ballistics, there are also a lot of grinding exercises that use the clubs' leverage -- which are fun, but not my main use.