Read Magic?

[Ganadai]

I was just reading over the Read Magic spell and got confused. In past groups we always used Read Magic to use a scroll that you normally would not be able to cast due to level/class. Normally if you did not have read magic you would have to make a use magic device or caster level check. However, reading the discription it sounds like you must cast read magic to "decipher" the scroll before the adventure (10min./level) and then "you are thereafter able to read that writing without recourse to the use of read magic." Does this mean that if I goto a spell library, use read magic on every scroll avaliable, then in the course of adventuring I will be able to identify and cast any of those scrolls that I might happen to find? Or does it only apply to the single scroll which I cast read magic on? If I use it on a mages spell book then can I use scrolls of the spells found within the book without a check? Or even if I use read magic on a lvl 9 cleric scroll and I am only caster lvl 2 do I still have to make a caster lvl check? I'm sooo confused!!!

[Ganadai]

1. Decipher the Writing: Requires either read magic or Spellcraft (DC 20 + spell level).

2. Activate the Spell:
- Must be the correct type of scroll (divine or arcane).
- The spell must be on your class list.
- User must have the requisite ability score.
- If your caster level is equal to the caster level of the scroll then no check is needed. Otherwise, you have to make a Caster Level check (DC 1 + scroll's caster level). If you fail that check you must make a DC 5 Wisdom check or suffer a Scroll Mishap. A natural 1 always fails the above checks.

[DarkStar]

I happen to answer my own questions very often. ;P But thanks for answering yours, it is useful to me as well.