... in the sense that it doesn't have the mass appeal of series like ASOIAF or WOT etc.

It's a fairly demanding series.

There's the fact in Erikson's mind, the universe and its mysteries as an integral aspect of the series, and he takes an anthropologic/archeologic approach: he leaves many clues, but it's up to the reader to reflect deeper and come up with his/her own theories. Some will be confirmed or destroyed by Erikson himself later on, some remain obscure even past the last book. You will get to understand the magic system, the cosmology too, much better as you go on, but beware... Erikson gives answers but new magic, new mysteries about the working of the world, or its history, keep piling up to the end.

Then there's the fact it's not as linear as most series. Erikson starts with a book with one cast in one location only to switch for the next one to a completely different set of characters in another location, and then returns to the first cast and so on in the third book. Mid-series, he introduces yet another (huge) cast on another continent, with a completely new set of storylines. It does all come together at the end (well, one the ongoing main storylines doesn't at all), but only after a fashion. There are tons of crossovers of characters from one set of players to one of the two others.

There are "main storylines", main themes, but most books offer their own story, their own structure. There are many shifts of tones and style. Erikson didn't stick to a single approach, rather he picked the one he thought most suitable, or that interesedt him the most to explore, for each book. Some books are very epic and broad - touching on either tragedy or myth - or will deal mostly with military campaigns, some books turn virtually mundane for some storylines, or philsophical, or even dabble a lot on juvenile dark humour, satire or the absurd. Some books have something like a quest, personal or more like a Hero's journey.

The first book is difficult. Some love it right away, some hate it but love the series, and some only get to love GOTM after reading a few more of the books and going back to it.

t gets much better on re reads. The first time, it feels like you joined a role playing game about wich you know nothing but you're among expert players who don't feel like getting you up to speed about anything. So you watch the show, getting what you can and missing a lot more.

In part, that's because it's a bit what the genesis of the book is. Erikson role played in the Malazan world he created with a friend for years, he knows it from top to bottom. He made it a bit rough for the novices. In part, it's because he wrote this book years before the others, and he didn't yet master storytelling. And in part, it's because Erikson had a massive amount of elements to put in place for the rest of the series (or even for his friend Esselmont's sub-series. It's rather amazing how much hidden stuff there is in GOTM.

It's an excellent series to experiment something really different, and if you're not looking for a grand unified and central storyline. It's a vast tapestry of stories and characters, tighly or loosely connected, set during events that span the whole series (and are, in many ways, the main storyline - and that's the one that gets concluded in the last book).

I would say if you begin it, try to at least read the first three books. If you're not a fan by then, it's pretty safe to say it will only get worse for you as it goes on and it's time to give up or lose you time with 7 more huge books. If you're caught up in the series by book 3, by all means go on. Each book is really different, so there's no telling before you read them which you'll like more and less (opinions differ massively among readers)