Disclaimer: I'm reading this book as a science teacher, so obviously my review comes from that perspective.
This clearly labelled student textbook teaches exactly the specification requirements for the AQA Biology course, while adding relevant examples.
An introductory section ('How Science Works') outlines the scientific method, and is followed by sections on each Biology topic from the course. Shorter closing sections cover the controlled assessment (a practical investigation that makes up 25% of the final mark) and explain the exams and exam technique. If you own the Chemistry and Biology versions of this book, you'll find that the non-Biology-specific sections are repeated in each book.
Each topic sub-unit, normally around 3 pages, explains the main points of a topic with plentiful diagrams, photographs, and key words introduced in bold text. Side bars learning objectives, and subject matter and exam tips. Practice questions help check that students have taken in the necessary information and can apply it. Full solutions to these questions are found in the back of the book - teachers' opinions will vary on whether including the solutions is a good thing. At the end of each topic is a checklist summary of the topic and exam-style questions (again, solutions are included at the back).
A glossary at the end of the book defines key words that have to be learnt.
I find this an excellent resource for self-study of the GCSE course - explanations given are very clear, and students can use the answers to check their own work. Whether it's the best main textbook to use in a classroom setting will depend on the particular group of students - but those doing separate sciences are likely to find it useful for independent study.