From inspection (without removing from the frame) it does not appear to be glued down on card as it shows lifting from the mount around the edges and the folded crease throughout the centre is also lifting. 

The front cover is discoloured and stained in places and is worn at both corners with small splits at the top and bottom of spine.
The gilt lettering is intact and in otherwise good condition.
There is slight foxing to the inside front cover and the illustrated first leaf.
There is also very slight foxing in a few places to the printed pages but the plates are not affected.

One coloured plate (The Crystal Gazer) has a small defect/loss of image to the tall column on the left.
All plates are present and the artists signature is original and in excellent condition.
Overall a better than average example.