Yes, the cover is removable. There are two velco strips at one end. You can take the foam strip out and clean it too if you want. 

Irishlass's statement that a disk herniation always requires surgery is false. The fact is that most people have some level of disk herniation later in life, but it often causes no pain whatsoever. Now. If you have confirmed sciatic nerve compression due to herniated disk material pressing on the sciatic that runs down the legs, surgery is often helpful, and sometimes required. Purportedly, there is a 90% chance of dramatic reduction in leg pain caused by sciatic nerve compression due to a herniated (ruptured) disk, which is called sciatica. Surgery is less effective for treating low back pain associated with a herniated disk.

You can use it in bed but I feel that it's most effective on the floor. I haven't read while doing it because I'm laying flat on the floor but it could be possible.

Yes I have fallen asleep on this mat before. Just watch it because you will have marks from sleeping on it. Also if you tend to move a lot in your sleep- I would avoid sleeping on it for long periods if time (I've given myself scratches by tossing and turning on the mat)