Bookshelves! Can’t do floorstanders or speaker stands.
As you’ve doubtless gathered, ‘bookshelf’ speakers usually sound pretty naff on bookshelves! But the possibility of success depends on quite a lot of factors, including:
What the shelves are made of.
What is nearby, such as a corner, actual books, rattling ornaments etc.
Whether the shelves are at the optimum height.
If you can run the cables there.
Can you wall mount instead?
Can you choose isolators or platforms to keep the speaker off the shelf.
Maybe a picture of your proposed siting might help. Have you heard the Prodigy models?