I think this should be explained further, as this is the most important part in order to ensure that you can access your funds again.

If you have a lot of books (and you can take care of them very carefully) you can use your books as a way to back up your seed. Choose 12/24 books, depends on your seeds (or just choose 1, 2, whatever you wish). In each book, mark a word (or a font) that represent your seed with invisible ink. To make it easier to remember, use the 1st page of the first book, 2nd page of the second book and so on. Take care of your books.

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And of course, this is not really the best way to backup your seeds. There are other alternatives.