I bought many books for my therapy practice. Do I expense them individually or as a group?

You can enter one business deduction for the books you purchased for your practice in 2021.    Since the useful life of books is greater than one year, they are technically assets and should be capitalized (entered into the assets section of your Schedule C).   However, you do have the option to expense these items, see below.   

When you purchase items for your business, you can either deduct the full cost of the expense at once, or you can deduct the cost over multiple years (depreciation).   The De Minimis Safe Harbor election lets you deduct the full cost of items worth $2,500 or less, instead of depreciating.    These elections are available for Schedule C businesses, rentals, farms, and farm rentals.

For instructions on claiming the De Minimis Safe Harbor Election in TurboTax, click this link - TurboTax Online Self-Employed