I usually scoff at books, and videos promising amazing results in 15 minutes a day. However, that does not stop me from buying them. My reasoning is, that while I might not be able to learn Russian in 15 minutes a day (if I learned anything in college, it's that becoming fluent in a second, or third language takes time - a lot of time), I might be able to glean enough Russian from a book making that promise, to qualify as an introduction to the study - and you have to start somewhere.
I wouldn't really expect to become toned and fit, in 15 minutes a day either. Again, I have enough experience with exercise to know that a 15 minute workout, that would provide real physical results, would be far more intense, and difficult, than I could manage. But, I might learn one, or two new toning exercises to add to my routine.
So, when I purchased a chronological Bible last year, with a statement on it's back cover, assuring the reader the entire book could be read in a year, in 15 minutes a day, I didn't really think it was true. After all, I'm a pretty slow reader. I read a lot, but I read it all very slowly. After, a couple of weeks of reading the daily portion though, I was amazed to find each section really did only take 15 minutes to read. It wasn't my first time reading through the Bible, but it was the easiest method I've tried.
15 minutes a day isn't enough time for a deep study, but reading the entire Bible in a single year, provides a big picture overview, that adds depth to additional study. If you haven't tried it, let me encourage you - reading the Bible in one year is a very doable New Year's resolution. And, it really can be achieved in 15 minutes a day.
It's great to be a homeschooler.