I’ve speed-read through this pron book by Kreidler. I would say that it makes good follow-up reading to Underhill’s Sound Foundations if you are inspired to dig into phonology even deeper. If you are only looking to get a grasp of phonology for the Cambridge Delta Module 1 exam, however, then Underhill’s title by itself would be enough.
Kreidler goes deeper into the science of phonology than Underhill, and provides lots of extra exercises to help readers understand and explore the concepts in the book. There are a lot of new terms presented beyond Underhill — far more than I’m able to recall at this stage. In fact, sometimes while reading Kreidler, I was wondering if everyone is using differing sets of phonological terms to express similar ideas, as the complexity of the discussion can get rather confusing.
Some of the ‘newer’ information involves offering more explanation around differences in dialect in relation to allophones. Early on, in Chapter 1, Kreidler explains it quite well in this excerpt:
Any speaker of English feels that the six words, geese, goose, glue, glee, greet, grew, all begin with the same sound. They don’t; they begin with the same phoneme which we represent as /g/. A phoneme is an abstract unit which is realized in speech as different segments in different positions. These different segments are the allophones of the phoneme.