I thought I had done this, but there is no 'Save' option that I can see, so it just reverts to the original description.
What's the process?
If you do a "revision" lulu makes a draft version. Look for that in My Projects. Revise the one that says that.
If all you need is to rewrite the book description, click on the book link in my projected and choose edit under that part. Then choose save.
The link to save your description changes is definitely there.