I would like to save it until its needed. Do I have to choose then and there or can I keep it for later?

You can keep it until it's needed.

No you don't ever have to read it

You can also take it out of your inventory - it's not a quest item. My Daedra worshipping Dunmer keeps it in a display case in Hjerim with Azura's Star. http://farm9.staticflickr.com/8016/7289336260_14e660e630_o.jpg

I like to place it on a Bookshelf in a Vanilla player owned home, then pan around to get a picture of my character standing by the Bookshelf<--- Makes the save have a visual reminder so it will not be deleted.

When you read it, it asks you something like "Are you sure you want to read it now or do it later." So it will be pretty hard (although not impossible, I'm sure) to read it accidentally.

I recommend that you use the glitch when you read it; that way you can keep it because it's unique looking.