Are any of the meals cookable in 15 minutes?
Don’t expect any 15 or 30 minute meal in a book to take that amount of time to cook the first time you cook it. You need to be in the habit of making that dish to make them to do them quickly.
I’m not sure of there being that many books of 15 minute recipes around. Jamie Oliver’s one is OK although I just take dishes rather than whole meals from it (mainly because my GF is veggie and I can’t eat dairy so a lot of the whole meal ideas don’t work for us)
Expand your time frame to 30 mins then theres an old Nigel Slater book of 30 min meals that might still be available (I bought min about 15 years ago) its focused more on suppers for two rather than meals to entertain and in fact the recipes range from about 5 mins to 30 and its more a book of quick ideas than dictating a whole meal.