One of these themes is that of isolation; Griffin- the Invisible Man- is, for the most part, cut off from the people around him. This is true both when he is in a populous city and when he is in small towns. Interestingly, it is also true that he is isolated even before he turns himself invisible. This is something he has done to himself; Griffin has cut himself off from other humans for a variety of reasons. One of these is paranoia- he fears that others will steal his scientific discoveries. Another is his hubris and runaway egoism: he thinks that he is better than everyone else, that his concerns are more important than other peoples'... he does not consider himself to be one of them. In the end, his invisibility is only the outward manifestation of his inward withdrawal from humanity.
When Griffin's self-imposed isolation becomes physical as well as mental and emotional, it is somewhat ironic that he finds that he actually needs assistance from others more instead of less. This results in his disastrous affiliations with Mr. Marvel and then with Kemp, who is ultimately responsible for his demise. But the failure of these associations are also the result of Griffin's attitude and behaviour; their cooperation is coerced by his threat- and sometimes application - of physical violence. Because of this, they are willing to betray him given the least opportunity to do so. Isolation can work both ways, and treating others as though they mean nothing to you will generally result in their feeling the same way about you in return.
When Griffin is relating to Kemp how he knocked a man out and tied him up in order to rob his house, he is shocked when Kemp takes issue with what he's done:
"Robbing! Confound it! You'll call me a thief next! Surely, Kemp, you're not fool enough to dance on the old strings. Can't you see my position?"
"And his too," said Kemp.
This is something which Griffin lacks: the ability to see how his actions hurt others, or care that they do.
I'm going to pause here; in part two of my review of The Invisible Man, I'll discuss a couple more issues such as the corrupting influence of unrestrained power and the dangers of science without ethics. I'll also discuss what- if anything- Wells' novel has to say about modern society.