Also forgot to mention that if you go to Butte via MT 41 and MT 2. Granny's Store is the only place to get food and water, and it's not that far from Twin Bridges. After that, you won't find anything until you hit the sprawl on the edge of Butte. There is no shade on MT 41, so if it's hot bring plenty of water. Climbing Pipestone, you can take a rest in the shade of the forest, but there was no shade on the road.
I suspect John is correct about the book being dated. A lot of the sprawl in Butte appeared to be relatively new. The entrance into town has a good deal of traffic, and because I-90 slices through the town, it can be a little tricky to navigate. I picked a route using Google Maps and it was pretty much a good one, but the way you go will depend on where you are headed in town. My route was based on getting to the Hotel Finlen in the Uptown part of the city, which is the historic part. If you are just passing through there is no need to go up there. (It's a good climb.) If you want to avoid a riding I-90 as much as possible, you need to take the frontage roads on the south side of I-90. A portiojn is unpaved, but it's easy riding. At some point, you cross under I-90 from Wild Horse Meadow onto Bossard (it looks like a drainage pipe) and follow that to interchange 211. We got on I-90 there for 3 miles to the exit for MT 1. Easy riding. Shortly after getting on MT 1 there is a nice new rest area with bathrooms and cold water.
Google Maps shows a road called Crackerville on the south side of the 211 interchnage that leads to a frontage road that ultimately leads to MT 1. However, if you look at Street View it looks like that road no longer really exists. Look at the alleged interserction of that frontage road and MT 1 and you will see what I mean. When I was out there I looked for the road and didn't see it. Whatever you do, do not take the idilic sounding Blue Bird Trail out of Butte. It's not a bike trail as its name suggests. Looks like it might have been a wagon or catle trail once upon a time. We had to walk some of it.