There is currently a bug with books: Newly bought books already have some content, you can't edit them. So keep your money for the time until it may get fixed.
It may also happen that given books appear with this wrong content to you. But they (hopefully) still contain the correct content for their real owner...
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P.S.: I gave away a book, got it back -- and it still contained the content with the helm parts.
Fortunately I already had a backup before weltall did not grant me enough time to make some.
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At the moment there are no more empty books and maps available from NPCs.
