James Blish's The Star Dwellers (1961) is a quality sci-fi novel (for younger readers) easily comparable to some of Heinlein's juveniles. The plot is straightforward/predictable yet still engaging. Of course, Jack, our seventeen year old hero, saves the day! Unlike the best "alien encounter" sci-fi novels which convey a certain sense of convincing "reality," The Star Dwellers demands the suspension of disbelief -- but that's not an issue since the short novel is clearly for younger readers.
Brief Plot Summary
The plot plays out exactly like an Original series Star Trek episode. Weird aliens (nicknamed "Angels") composed entirely of energy are discovered in a distant region of space. They accidentally destroy a few Earth vessels when they attempt to inhabit their engines (a source of energy). However, one "Angel" voluntarily comes back to Earth (inside one of the engines). The commercial sphere of space travel sees great benefit in employing these ancient beings because while they're in the spaceship drives they're able to make them run more effectively.
Jack Loftus is a member of the Space Cadets. This highly selective group of boys are assigned to various secretaries and given highly important tasks to perform. Think Wesley Crusher... Jack, a second space cadet, and Field Agent Langer, are sent out to make contact and sign a treaty with the "Angels." The entire system makes little sense because Jack has NEVER piloted a spaceship and clearly doesn't have the experience to undergo a mission of such importance -- but, that's besides the point...
Agent Langer and the second space cadet set off in a small solar sail vessel to make contact with the aliens leaving Jack alone in the main spaceship. The entire situation is complicated when the aliens make contact with him instead! Are their intentions good? He is unable to reach Langer! It's up to Jack to figure things out!
Blish rarely bogs down his narrative with endless political preaching which characterizes so many of Heinlein's juveniles. Only when everyone is bored on trip to the area where the aliens live do any of Blish's political leanings emerge. On the whole they're quite benign -- besides, as expected, his view that women serve only to distract men during their most important time of learning. Unlike Star Trek's Starfleet there are NO female Space Cadets. There's one female character, a young news reporter, who attempts to follow them. Although she is unsuccessful in her mission, she does play an important part in saving the day at the end.
Don't expect convincing aliens, deep philosophical discussions, interesting technology, or strong female characters. The Star Dwellers is a fun, (mostly) politically benign, juvenile space adventure tale with a positive moral message.