Let us assume you purchased a book with significant historical significance , an association copy from the library of a president. It would be a crime against future generations to remove the bookplate. On the other hand, if you went to a library book sale and got a Reader's Digest Condensed Book with a bookplate you wanted, the removal would be completely acceptable.
It's all very subjective .Over the years I have ,in fact, removed many bookplates.
Sometimes the books are donated to a charity, sometimes they are resold on ebay.
Here is the way I remove the bookplates without damaging the book.I would suggest that you start by practicing on distressed items.These instructions should not be used for leather bookplates and those with red dye should be tested first with a moistened Q-Tip, as red tends to bleed.
1) Boil Water
2) Fold a paper towel in quarters and cut it slightly larger than the bookplate
3) Using tongs, immerse the folded towel into the boiling water.
4) Place the steaming towel on top of the bookplate. If the bookplate is on the inside front
cover be sure it is level. You may have to place a saucer under it to keep it level.
5) Wait two minutes and place the point of a knife under a corner of the bookplate. Lift gently
and try to pull off.If you encounter resistance continue to soak another minute.
6) To avoid curling, after removal , place the bookplate betweeen some paper towels ,
place a book on top and let it sit for a day.
Let me know how well this worked for you. From time to time you may be surprised to find a second bookplate under the one you removed.
That's all for today.