To get The third tablets, I need 4 glowstones, one is to open first corridor at the rotated room ,two is to open second corridor at the rotated room, and need two stones to open secret chamber. But I can find 3 glowstones, where do you get another one glowstones? or do you use teleport spell?

Only 3 that I've heard of -

WEll, according the the strategy guild which was not worth the expense and shipping, you can actually use a glowstone more than once. The book suggests that after you have completed the east area that you can take back the glowstone you used to open that area and use it elsewhere.
Or, you could find something to block one of the two doors, take the glowstone and to open the other door in the two door puzzle.
Did that make sense? Well, hope it did.

Wyv

Thanks to your reply! Puzzle!,I understand! Thanks!