I'm currently struggling 200 pages into Blue Mars. Great series though (I'm struggling with it due to life getting in the way, as opposed to it becoming a grind - although there's a bit of that too, but it's three 700-odd page novels...)
However, there is a very efficient trajectory that could be used by solar sailing ships for a fast, cheap route to Mercury once every 16 months. You leave Earth for Venus, where you do a gravity assist to drop your perihelion significantly below the orbit of Mercury, just to get low enough that a reasonable solar sail can get reasonable thrust even with significant cargo. Then you can use your infinite delta-v to match your aphelion with Mercury, and can do an efficient capture trajectory.
Based on MESSENGER radar data, the Mercury south pole probably has more water than Mars. The temperatures at most of the craters would also support CO2 ice, although our current data can't prove it's existence or rule it out. Nitrogen supply would probably be rough.
One of the interesting reasons to consider Mercury for colonization is that a colony on the inside rim of a crater would have very easy access to energy in many forms. Want natural-ish lighting? Raise a diffuse reflector on a pole. Want to melt something? Raise a mirror.