Shut down completely the read/write head moves to a parking zone where it won't damage the media with a jar. (it could still be damaged with a big enough slam, but the media should be OK and it can take a lot more shock that way) I don't know if sleep mode will do the same - it should, but I wouldn't trust it, if some engineer had the bright idea of saving a few milliseconds on waking.

Large books are a pain in the neck to strap on a rack, but doable. Keep the laptop in the backpack. I carry my work laptop in a notebook hooked and lashed in the pannier position, very convenient, but it's only once in awhile not every day and I've done the commute often enough that I'm not likely to crash it.