It really worked for me, I lost about 2 stone on the 5:2 where I'd struggled with slimming world, calorie counting etc before. I am small and old with a pretty low TDEE (total daily energy expenditure, basically the amount of calories needed on a daily basis to maintain weight). I enjoy carbs, eating out, alcohol, treats, basically all the things a lot of diets forbid or severely restrict! BUT, crucially, I also naturally very much incline towards eating 1 or 2 meals a day, not little and often/grazing so this way of eating always made sense to me, on things like SW I was making myself eat when I wasn't actually feeling hungry, e.g. first thing in the morning to fit the 'plan', but it didn't seem to be making me less hungry at other times if you see what I mean and I hated having to have separate dinners to the family or not being able to have what I wanted when we ate out. Fasting suits me much better in that respect but not everyone feels the same at all so you need to see how you feel on it I think. To be honest, I find the harder part being to stick to eating sensibly on the non fast days, even though you are eating technically what your body needs (not depriving yourself) on those days, if you are used to eating a lot more it takes some adjustment and discipline to stick to it until you get used to it.
A typical fast day for me on the 5:2 (500 cal days, twice a week) would be just black coffee, herbal tea and water in the day (no breakfast, no lunch), then an adapted version of whatever the family was having for dinner. 500 cals actually gets you a pretty decent portion of most typical family meals e.g. stir fry, curry, pasta, stew. I sometimes reduced the carb portion down and had extra veg instead, or just an overall slightly smaller portion. If not eating with family for whatever reason calorie counted ready meals were very handy!
On weekday non fast days, I try and eat sensibly within my (very small!) TDEE, usually no breakfast (as above this suits me, but you can of course eat breakfast on this diet if you need to), a light lunch of soup/salad/sandwich and some fruit for about 400 cals, typical family dinner for 500-750 cals, some more fruit or yogurt for afters, usually then leaving some room leftover for a small treat for 200 cals ish. I would then have a 'treat' day at the weekend where I might have fry up for lunch, roast dinner or takeaway for dinner and then some drinks or snacks in the evening, usually ending up 500-1000 cals over TDEE, but still losing weight providing I stuck to the plan on the other days, which is pretty great IMO!
If you are interested , there is a wealth of information and some very supportive threads on the 5:2/fasting boards, meal ideas, exercise threads etc., head on over and take a look?