When I was about 13 or so I first read
Rip Foster Rides The Gray Planet. I remember that I loved it. It still holds some interest. Goodwin writing under the pseudonym of "Blake Savage" creates an exciting plot which has more of a "science" element in it {at least by 195os standard} and the characters show a wider range of cultural ethnicity than we find in the Tom Corbett series.
Politically, the world of Rip Foster is quite dated. The bad guys are citizens of the "Consolidation of Planetary Governments" . They are usually simply referred to as "Connies". Hmm--I wonder whom we are supposed to be reminded of now.
Rip and the rest of the good guys come from the "Federation of Free Governments". When the Connie soldiers are invariably defeated, they itch to defect to the land of their captors.
That said, there's quite a bit of nostalgic entertainment in this little novel.
The book is included in the Kindle
Tom Corbett Megapack along with the seven Corbett novels,
Star Born by Andre Norton and
The Secret of the Ninth Planet by Donald A. Wollheim. This Megapack is well formatted and you get good value for the low price. However, the Corbett Novels are available free here on MobileRead and in Project Gutenberg in editions which include the original black and white illustrations--absent in the Megapack edition.
Rip Foster with illustrations is also separately available in PG but the formatting isn't as good as one would expect.