Offical ACT Prep Guide vs. Barron's ACT vs. Barron's ACT 36

I’m taking the ACT in September and I’m just wondering what book would be the best to raise my score. I got a 29 when I took it in June and I’d love to get in the 30’s this time around. 33 would be my ultimate goal, but anything between that and 29 would be good. I’ve heard the Barron ones are difficult, but I feel like that would better prepare me because then the actual test will seem easy in comparison. I’ve also heard people using both the official guide AND the Barron’s ACT. But to go from a 29 to a 33, what book/books would be the best to achieve that? Thanks!