I don't presume that all people realise that Les Mis is entirely sung through. In fact, the first time I ever saw it at the theatre, (a very long time ago, before google, and at a time when I wasn't confident enough to ask the ticket agent what it was about,) I knew nothing at all about it, and even thought that it might have been in French! I went anyway. It was the first West End show I ever chose to see, and I chose it on the basis that it had been a permanent fixture at the Palace theatre for forever, it seemed, so I figured it had to be good. I can't tell you how relieved I was when the opening bars revealed that the language was English.
That it was entirely sung through wasn't an issue at all after that, and the fact is, that if you love the music that they are actually singing to, the constant singing isn't going to bother you at all. This is the only completely sung through musical that I actually like, to be fair. With the exception of one song, I hated Jesus Christ, Superstar and I didn't enjoy Evita much either. It's not because they were sung through. It's simply down to the fact that the music doesn't captivate me the way Les Mis does.
But because I know that the constant singing is not for everyone, I make it very clear to anyone that I recommend it to that it is completely sung through, so that they know what they're getting. I loved it from the very first time I saw it, but I know that for others, they would probably prefer to take a bath in cold sick than to watch something like this.