There actually is confusion over this title. For one this is not the work where Galileo defends Copernicus (Heliocentrism) where the sun is the center of the universe or the solar system. That work is called "Dialogues Concerning Two Chief World Systems" (1632).
This work, "Dialogues Concerning Two New Sciences" (1638), is about Galileo's experiments in bodies and motion.
The publisher is not wrong at all in calling this work the given title of "..Two New Sciences". If anything it is Galileo's and his original Publisher's fault for naming both works in such a similar fashion: "Dialogues Concerning Two....." The biggest difference is in the last words of the title.
For those concerned with Copernican/Aristarchus of Samos vs Aristotle/Ptolemaic dialogues (sun vs earth as the center of the universe/solar system) for which Galileo is known for please read Dialogue Concerning the Two Chief World Systems (Modern Library Science)
For those interested in Galileo's physics of bodies and motion and the book , as he said, that "contain results which I consider the most important of all my studies" then "Dialogues Concerning Two New Sciences" is the correct one.
For a general sample of many of Galileo's works and related documents from his "controversy" from those who did the trials on Galileo, please read : The Essential Galileo. Look also at Galileo's Sidereus Nuncius, or The Sidereal Messenger for his observation on the surface of the moon from his telescope.
A few similarities between both books by Galileo with similar titles have laid confusion to some of these reviewers:
1. as was mentioned, both begin with similar titles: "Dialogues Concerning Two....."
2. Both have the same picture of 3 men speaking
3. There are 4 days of dialogues in both books
4. The same three characters are found in both books: Salviati, Sagredo, Simplicio
These similarities between both books are what makes them so hard to distinguish for anyone who has not read either one of these works. So confusion and disappointment are expected. I too got confused until I got copies of both assuming they were both the same. I wanted a better copy of "Dialogues Concerning Two New Sciences" and bought "Dialogues Concerning Two Chief World Systems" since it was cheaper (by very little). I read the Copernican heliocentric arguments that are only found in "Dialogues Concerning Two Chief World Systems" and noticed that "Dialogues Concerning Two New Sciences" was different and did not focus Copernicus at all, but instead focused on motions and bodies.
Hopefully this post clarifies and saves people from buying the wrong book. In any case, I say get both books since "Dialogues Concerning Two Chief World Systems" IS notable and important (but definitely not revolutionary since defending Copernicus was not done in an empirical fashion, but was done more in a theoretical and investigative fashion where the debating is over interpretation of previous evidences and data, not over newly generated data and results from experiments by Galileo). "Dialogues Concerning Two New Sciences" gives insight to the mind and experiments of Galileo along with his debates on the nature of bodies and varieties of motion.
For those interested in some the works Galileo discusses in "Dialogues Concerning Two Chief World Systems" please look at Ptolemy's Ptolemy's Almagest, Copernicus' On the Revolutions: Nicholas Copernicus Complete Works (Foundations of Natural History), and Aristarchus of Samos' Aristarchus of Samos: The Ancient Copernicus (Dover Books on Astronomy).