The OpenStax series are free. I've found the explanations very clear and detailed: https://openstax.org/subjects/math https://openstax.org/subjects/math Some

The OpenStax series are free. I've found the explanations very clear and detailed: https://openstax.org/subjects/math https://openstax.org/subjects/math Some are even downloadable to a Kindle (for free) on Amazon.