How can I make a good bookshelf/book storage on a very limited budget

I am currently out of work, a teacher with a son who needs a lot of reading and writing practice, with a husband who stores office catalogues in the house due to limited office space. We live in a small rental apartment so can't make changes to the house. I'd like to organize my limited space but can't spend much so I need all budget-friendly space-saving ideas I can get. If possible, I'd also like ideas on how to make a bunk bed with sufficient storage.

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