I've been cooking Indian food for nearly 25 years, have a good dozen Indian cookbooks on my shelf, and have cooked about a dozen recipes from this book, and I can honestly say, this is a VERY bad cookbook. There are so many problems, many of which seem like an editor could have addressed but many of which lie in the fact that these are simply bad recipes.
The most obvious issue is the vague ratios. "2 large onions" is a common way to refer to the amount of onion in a recipe, however, a large yellow onion in the U.S. and a large white onion are vastly different. You're easily talking a difference of more than a cup of onion, which will obviously have a drastic impact on the final dish! This comes up a lot. "Leaves from one bunch of methi" is used in the aloo methi recipe, but there is no standard for the size of a bunch of methi and the amount can easily differ by a whole cup. This comes up over and over and is simple to fix. Just measure the amount you used in the test recipes and print those amounts! I realize a counter-argument would be to just improvise, but if this is actually supposed to be a definitive course, then you need to teach specifics first before your student can successfully improvise. That being said, in every recipe I've tried I've had to adjust things, often things which are just basic cooking fundamentals regardless of whether it's Indian or Italian cooking. This leads me to point number 2...
One can often just read a recipe and see that it is wrong. For example, a veggie recipe calling for sautéing the veggies will have too little to prevent scorching or prevent the meat from adequately searing and not sticking. Cook times are often waaaay off. That aloo methi was supposed to take 25 minutes to cook, but following the recipe exactly it took nearly 90 minutes for the potatoes to become tender. In many cases, it's the opposite. A number of shrimp recipes suggest cooking the shrimp until pink and then simmering for 10-12 minutes. NOOO! That will give you shrimp as tough as rubber. Chicken breast recipes that call for browning cooking bite-size cubes of chicken breast for 4-5 minutes and then simmering for up to 15 minutes? Do you like dry-as-sand chicken breast? The mistakes and poor techniques show up over and over.
Lastly, perhaps the greatest sin is just how bland all the recipes are...the spice amounts are almost always far too low for the amount of meat and veggies called for resulting in some really disappointing dishes that are honestly an insult to Indian cooking. Is it dumbed down for western tastes? I don't know, but even the amounts of salt are always too low. Good Indian food does not need to be hot, but by god it should have a spice profile with decent depth and dynamics of flavor. This is indeed a lovely book. It looks sooo much better than some of my favorite Indian cookbooks, but make no mistake, this is not just a terrible Indian cookbook, it is a terrible cookbook in every way, regardless of style. I just ended up tossing it in the recycling bin. I didn't even bother selling it or donating it - no one should be exposed to such poor recipes from such a glorious cuisine.