The Indian Slow Cooker, which has been pretty brilliant. If you're looking to introduce some new recipes to your repertoire, this is a good book to get, especially if you like spicy food and if you are looking for more vegetarian recipes (though there are good meat recipes as well).
What I like about this particular cookbook is that it provides a good variety of things you can make; there are a lot of bean dishes that actually taste good (I'm sorry, but all too often, urging people to eat "rice and beans" is sentencing them to a gluey, tasteless mess). I've made moong dal in the slow cooker with good results. I've also made South Indian Red Lentil Curry (pictured) which uses coconut milk. Which is pretty darn close to bacon in making everything taste good. If you want to go meatless or cut down on the amount of meat you eat, or if you just want to try something new, this is a good resource.
Some of the things the author asks you to get may seem onerous if you don't live in an area with a large South Asian population and the attendant grocery stores (if there is an Indian grocer near you, definitely check it out. And get a samosa. Those are from heaven). You can find many of those spices--albeit in smaller quantities and for more money--in a grocery store, but if not, you can order them online. The beans that the recipes call for do tend to be found mainly in South Asian grocery stores. We do not typically eat black lentils here, or skinned an split yellow lentils, or black chickpeas (with the skin on), etc. But again, you may be able to find a source that you can order them if you like, or you could probably replace the beans with a reasonable substitute. Red lentils cook down to a very creamy consistency and could probably be swapped out for other skinned, split lentils if you want.
This dish took about seven hours to cook--I used a timer from the hardware store to have the slow cooker go on at 11:00. It was very, very good. I was looking forward to leftovers. I froze some of them so I wouldn't gobble them all down at once.