I regularly use this series of books for language learners. This particular book is so useful not only for the grammar and vocabulary sections but also for the functional section. It gives the language we need to cope with specific situations; for example telephoning, booking rail or bus tickets, asking for directions etc. With the key at the end of the book, I recommend this for students who want to continue studying by themselves when they return home as they can check their answers with the key.
As an English teacher in a high school I've found it quite useful to review vocabulary, useful expressions and writing. It's got clear examples and explanations. Some exercises can also be used for A2.