I don't have to look any further than this textbook to find out why my son finds mathematics boring. This is a textbook that has a glut of exercises that includes some interesting and in some cases very challenging questions, but lacks any logical structure and is very poor when it comes to explain how to do things.
This book (book 2) represents a second year of an IGCSE course. In the case of my son, it is being studied in year 10.
The book is made up of 5 units. Each unit has Topics classified as number, algebra, graphs, shape and space, and manipulating data. In other words the remainder of the IGCSE course has been chopped up and inserted pretty much at random, with the exception that one of the categories listed appears in each unit. So, each chapter in question doesn't really follow on from previous chapters.
If you look at any chapter in isolation, there is very little explanation and no real introduction at all. My son is currently studying Algebra 2 (Quadratic equations). He did some of this last year, and fortunately for him, I taught him some using a different book recently. In this chapter there are two sentences to introduce the topic, Some information in a box entilteld "Remember" to tell you different ways to factorize, and a couple of worked examples. This is followed by a number of exercises with in excess of 20 questions in each. In all there are 14 large exercises in this chapter with very few examples.
If you look at the book as a whole, in general it follows the same pattern described above. Even for me, this represents a really boring and uninspiring textbook that does not explain clearly how to do things. With such a text book the student is totally dependent on their teacher, who presumably just uses the book as a source of questions to set their students.