Battery monitor for a camper van electrical system
You want to read bi-directional current (battery charge/drain), which means that the INA139/169 with a shunt is out.

Based on the current range, you probably want something in a high range:
http://www.allegromicro.com/en/Products/Current-Sensor-ICs/Zero-To-Fifty-Amp-Integrated-Conductor-Sensor-ICs.aspx

There is an alternative breakout board from Sparkfun: https://www.sparkfun.com/products/8882

It only has a range of 5A, though.  You might want to find a friend in the local hackerspace who can layout a board and show you how to solder a higher current part.  I have used the ACS711 and ACS712 in the past, they are great - and simple - parts!

Also, generally, it is best to sense current on the high side.  This is b/c when you place resistance in the return path, all of the circuit 'above' the current has a higher resistance path to ground and tends to generate more noise.  It is done, no doubt, but on as small a part of the circuit as is possible.