The story is enjoyable as soon as you start picking up on the pace. The beginning chapters may appear a bit useless in terms of plot development, but in the end they really are essential to the story. People who drop this manga because it's "boring" haven't reached the point where exciting events are brought upon our main couple by the side characters yet. To be honest, I was about to drop this at around 10 chapters in, but decided against it. That was a great choice on my part, because this story and its characters develop at the same pace you fall in love with it. Every character has depth and some aspect of realism; though abiding general shoujo stereotypes (such as the bad boy, the nerdy girl, the pretty female friend etc) our main characters are so unique and well thought out that despite how strange they seem, it appears they're perfectly capable of being real people!
As previously stated by the other commenters, no one is despicable or generally antagonistic in this story, and as the love polygons shape you can't help but root for all the different characters to succeed with their love.
This said, love is another huge topic in this manga. Not clearly defined and not a hundred percent known by our characters, love is shown clearly with how it is in real life. Unlike most shoujo manga where love appears and our characters are completely aware of it, Tonari no Kaibutsukun shows how love in reality is ambiguous, and the transition into love is never really immediate either.
I won't say this manga is realistic, for obvious reasons regarding manga, but how the mangaka develops the characters and the relationships really mirror what happens in reality. Story-wise, this manga deserves a 10/10.
Aside from the story, the comedic side panels and odd occurances could make anyone chuckle, especially when they're made to soften the mood after a rather serious chapter. The art is beautiful as well, and the mangaka successfully brings out the emphasis in scenes where emotions are shown clearly by the way the faces are drawn.