This is a great idea for a product, and as it turns out, it's a great product as well.
This isn't an attempt to reinvent the wheel. The assumption is that you will get or already have the original classic version of the adventure. What this book does is give you some ideas on what to play up and where, points you to where the monsters are in 5th edition, swapping out as needed, substitutes what magic items you might need for treasures, and converts the unique aspects of the adventure, such as singular monsters and NPCs.
These are broken out in several pages of descriptive text, and then summarized on a cheat sheet.
What impressed me, and what I wasn't expecting, was the nice, short section on converting the adventure to the Realms, complete with what fallen empire is appropriate and what deities should be swapped to customize the adventure.
I really look forward to more of these. I think this is a great product and a great idea.