As a textbook, it is very lucid and detailed (something which not many books manage to do together), and is definitely helpful for students of English Literature.
That said, don't be uncritical of the book's perspectives. So, I know that, since English is the language of a White people, the authors are most likely to be white. BUT, the twentieth century, after colonialism, has seen such a boom in English writing by non-white folk, to a point that more English authors are black or brown or Asian than white (yes, this is true). Which means, the last quarter of the book, which addresses the 20th century, and COMPLETELY ignores the multitude of Black and Asian writers who wrote and write in English, is essential reductionist and amnesiac. I mean, for a language that is as rooted in colonialism as English is, can you really talk about its modern literature without talking about postcolonial literature? To talk about late 20th century literature, and to not mention Black authors like Chinua Achebe or Toni Morrison or James Baldwin even once is an epistemological crime, in my humble opinion. And the argument that the book is about British and Irish authors only doesn't hold up, because it clearly isn't. It spends reams talking about American and Australian literature, not to mention that there HAVE BEEN important writers of colour in the British isles too!
Secondly, the authors have a preference for bourgeois works of idle literature, which comes through in the section on Modernist drama: thus, works of political realist theatre about the visceral experiences of working class youth in the 1950s is seen is inferior literature in contrast to the idle existential theatre of Samuel Beckett where nothing happens and only rich people will enjoy (since only they have the luxury to muse about existence and its meaninglessness, since they are not occupied with a constant fight to survive). I'm not saying Beckett isn't great (I mean, I loved Waiting for Godot), but what's with this hierarchy of art? I can't help but detect an elitist bias. Still, this is more an ideological opposition on my part than a technical flaw.
Lastly, the terms of literary theory (Modernism, post-modernism, humanism, feminism, Marxism, etc.) have not been used very precisely ot academically, although perhaps that is not a huge drawback for a beginner's textbook. The lack of proper jargon is a two edge sword, but is admittedly helpful upon first reading.
All in all, still a great textbook, and general repository of knowledge. I hope they correct their race issues in the following editions, and it might just be perfect.