Research
I've been doing lots of research via the web, since the only books I've been able to find are Japanese (understandably) and are then only available through Amazon Japan. I'm pretty sure a friend of mine in the UK bought some movies from there though, so if I can be confident that Book X has lots of helpful pictures then it might still be an option. But for the moment, the internet suffices.
Fitting together the photographs and working out which are different views of the same place, as opposed to views of different places, has been quite fun. Like doing a jigsaw puzzle without the picture, and with all the pieces the same shape.
The following have been particularly useful:
The railway photo archive at nekosuki.org (translation). On this page, the pictures start at Kamakura and work along the line to Fujisawa, which makes them easy to follow.
Pictures on Flickr, although these tend to be more arty and less informational than the Nekosuki pictures.
Google Local, which has maps of the area down to 1 pixel : 1 metre resolution with outlines of all buildings and real-colour aerial/satellite imagery at the same resolution. It even shows the trackwork accurately. I took about 20 screen captures to paste together a composite map of the whole line. (Key stations: Kamakura, Hase, Gokurakuji, Enoshima and Fujisawa.)
Even better than the maps, you can drive the route yourself using Boso View Express (BVE) for Windows'XP, and the Enoden route and train files. You'll need to follow the instructions about changing the [PressureGauge] entries if you want to use the route with BVE4. It's not the most fancy-looking simulator ever, but it works really well and makes it easy to put the pieces together in your head. And it's free!
If you're going to be following any of these links, you may like to look at this schematic map to get your bearings. It's roughly to scale, although obviously all the pointwork is hugely scaled up to make it visible, but it shows how the line skirts around the coast and the relative positions of all the stations.
