I discovered this book through a 1927 ad in The Gregg Writer, which recommended using it with the 1917 Speed Studies after completing the portion of Speed Studies coordinated with the 1916 manual. OK, I' curious by nature and ordered a copy of this book for about $5 including postage from an eBay seller. It's a great book! The syllabic density of the words (which are conveniently counted in groups of 10) gradually increases. There's over 400 pages of business letters, reporting and literary material with -- if you're familiar with other Gregg dictation books -- shorthand previews of words and phrases in the margin beside the printed letters. The volume is clearly for a student who's completed and practiced the theory as from the very first letter the learner is thrust into brief forms and intensive phrasing. I'm tickled pink with the publication and heartily recommend Rational Dictation by McNamara & Markett for anyone wanting more Gregg practice material.
Caution: Although the previews are in pre-Anniversary, that should be of no great hurdle to anyone who has actually studied any version of Gregg and wants to improve his or her shorthand vocabulary building. This is a super book!