This book is concerned with the meaning and use of two kinds of declarative sentences:

1) It's raining?
2) It's raining.

The difference between (1) and (2) is intonational: (1) has a final rise--indicated by the question mark--while (2) ends with a fall.

Christine Gunlogson's central claim is that the meaning and use of both kinds of sentences must be understood in terms of the meaning of their defining formal elements, namely declarative sentence type and rising versus falling intonation.