https://leanpub.com/mastering-stm32-2nd https://leanpub.com/mastering-stm32-2nd This is good book to start learning. Don't worry too much about using HAL. You

https://leanpub.com/mastering-stm32-2nd https://leanpub.com/mastering-stm32-2nd This is good book to start learning. Don't worry too much about using HAL. You can dig deeper by implementing HAL functions yourself. The thing is if you are making a product, using a HAL is generally a good solution. Also keep datasheet of specific microcontroller nearby.