A book that forms part of a series that is a must for all SF fans. If you want to be critical, then the stories could be said to lack true literary depth, and the authors handling of the relationship between the hero and his love can best be described as "twee." But the overall book and indeed the whole Lensman saga is a rip roaring deep space adventure that takes scientific speculation from the 1930's and presents them in a way that is still believable in the 21st Century. It really is a superbly fun story about Kimball Kinnison (the hero) who is a kind of Super Space Cop fighting the villains (Boskonian Pirates) in one gripping encounter to the next. The authors imagination runs riot in speculation of non-human species inhabiting our galaxy, and the inspiration for the subsequent Star Wars movies of the 1970's/1980's is clear (although I have yet to see an admission from George Lucas to that effect).
I recommend that SF fans start with this book rather then the 2 earlier books (Triplanetary and First Lensman) because the original inspiration for the series was the exploits of Kinnison, and it makes it more enjoyable to follow Kinnisons exploits and the true core theme of the series first (the adventures continue in Gray Lensman, Second Stage Lensman and Children of the Lens). Then the reader can read the preview books to complete the series (remember that Isaac Asimov did this with is brilliant Foundation saga and it made it more interesting to read the books in the order they were written). True Lensmen addicts can then dip into Masters of the Vortex (also called Vortex Blasters) which is as relevant to the main stories as The Horse and His Boy was to the C S Lewis Narnia Chronicles (i.e. just a sub plot filler).
So whilst not a perfect literary work, this is a hugely readable, unputdownable, essential SF Space Opera for SF fans everywhere and deserves the full 5 stars for being the first and ultimately most original Space Saga.