Do a search for previous FF threads, as there should be plenty of info out there. I lasted about 38 days almost exactly a year ago, and it wasn’t fun. Effective, but not fun. And you can combat the rebound by titrating carbs back into your diet in the week or two after you finish.
I modified my diet a bit, adding just a smidge of high-fiber veggies or flax fiber every meal or two. I also incorporated psyllium husk twice per day.
For an even sticter version, check out the Protein Sparing Modified Fast…you should be able to google it.
The reason both of these have there place is because, in my opinion, they give the dieter a lot of bang for the buck in the first few weeks. There’s nothing worse than suffering through a new diet only to see minor changes in the early stages.
But remember, neither diet is a panacea. You still need to get your long-term eating plan in place.