A previous reviewer suggests that the book instructs you to buy ready-made lamb tikka pieces - I think the confusion lies in the fact that there is a recipe for lamb tikka that teaches you how to prepare the meat in the style, that can then be used in other recipes, and it was this page that the reviewer missed in their enthusiasm for their favourite meal, so they were left with the assumption that they would have to buy the tikka meat.
Regardless, I have found this book to be entirely instructive and helpful in creating food that is usually very unhealthy, but in a controllable environment. It is now a little easier (and better for the waistline!) to have quick and easy food more than once a week, especially safe in the knowledge that you know exactly what went into the dishes! Brilliant.