Best book for ACT and SAT Prep

Title says…
Please suggest best books for ACT and SAT prep
TIA.

My kid looked at Barron’s ACT 36, because that’s the only one our local library had. He said the English section had some really good tips, math not so much.

Best approach is to take an old test (you can find these free online), and see what the baseline score would be. Then focus on individual sections as needed. Khan Academy is helpful for SAT, I hear.