Luckily for those of us inclined, the Maine 2-Footers are well documented, and for SR&RL buffs, it is particularly well documented. I'll try to list all of my books on the SR&RL in my library with a short review here, and include those that I have from the other Maine 2-footers as well. Also, I have one or two books on the Bedford & Billerica RR, the mother from which all the others were begat, and I'll list those as well.
Two Feet Between the Rails
By Robert C. Jones. Someone on a Facebook group not too long ago asked what the best single volume history of the SR&RL for a model railroader to get started with was. I told him it was this two-volume history. Why? Because there is no best single volume history that is useful for model railroading. The best single volume history for reading is The Maine Scenic Route. If your goal is a visual representation of the railroad, you need photos with captions. Lots of them. This two-volume history covers both criterion; verbal history and captioned photos. So if you're modeling the SR&RL, and get no other books at all, get these. You'll notice that there are bookmarks sticking out all over the place in the photos of mine. That's because I refer back to them all the time, more than any other books on my shelves.
The Maine Scenic Route
By H. Temple Crittendon. Ok, if you want a single-volume best reading history of the SR&RL, it's Crittendon's. When I was a kid, building my first (HO) layout on a sheet of plywood in the basement, I found this book in the school library and fell in love with the Sandy River & Rangeley Lakes RR. Even though I grew up a mere 30 miles away, I had no idea the railroad had existed. The old roundhouse we used to drive by on the way to Rangeley was simply "from the railroad that used to be here"' I don't remember how many times I checked the book out, but I do remember that it inspired me to scratch build a "2-Footer" box car, that I dreamed would someday go on my dream SR&RL layout. So here we are.
Maine Two Foot Pictorial SR&RL Freight Cars
By Gary Kohler. Great reference for quickly identifying the types and details of the various freight cars used by the SR&RL. For more detailed descriptions and more photos, refer to Jerry DeVos books, but if you want quick answers, go here first.
OTHER MAINE TWO FOOT RAILROADS
Industries and Operations of the Maine Two-Foot Gauge Railroads
By Peter S. Barney. I think of this as a companion boot to Industries and Operations of the SR&RL, but no doubt those who are more into the other railroads feel just the opposite.