Did you change your mind after adding a title in a Space? No problem: you can easily remove any recommendation you've made in a Space.
Here's how:
From within a Space tap on the three-dots symbol next to the title you'd like to remove from that Space.
Now just tap on "Remove recommendation" and you're done.
Please note: even as a Space owner you'll only be able to remove the titles you've added to a Space yourself, not the recommendations of other members.