I've always wanted to read this book and have seen it prominently placed on bookshelves in all major bookstores. Personally I was quite disappointed and found the book difficult to read.
I know it was originally published in 1989, the language / writing style was a little different but my main gripe was that there was the lack of word economy. I felt the chapters / concepts contained excessive elaboration which felt repetitive. There was a lot of personal stories / anecdotal evidence but very little scientific evidence cited to support the concepts. Personally I like books which are supported by science and statistics, e.g. Charles Duhigg's: The Power of Habbits.
I don't necessarily disagree with the 7 principles outlined in the book, I did like Habit 2: Begin with the End in Mind. But I can honestly say there was nothing ground-breaking in the book for me. I also don't doubt that Frank and Stephen Covey are brilliant life / business mentors. But this book felt really dated to me and there are far better books out there if you're looking for principles / actionable insights e.g, Ray Dalio's: Principles.