Man, I just went down this rabbit hole trying to figure this out. So, 'The Maddest Obsession' isn't floating around free and complete on any official site that I've found—it's published by Bloom Books, which means they want you to buy it. You'll hit a wall after a sample chapter on retailers like Amazon or through Kindle Unlimited if you have that.
There's a ton of sites that claim to have the full PDF or let you 'read online for free,' but honestly, they're sketchy. The formatting is usually messed up, missing paragraphs, or worse, riddled with malware ads. I got a pop-up once that nearly gave me a heart attack. Plus, it just feels wrong not supporting the author, you know? Danielle Lori wrote the thing.
Your best bet is a library app like Libby. That's how I got my hands on it legally without paying. Had to wait a couple weeks, but it was clean and the app is solid for offline reading.