It isn't like reading a book, though, and in a way which possibly responds to your "slowness" worry. Some days, the installment is quite short. This is today:

Jonathan Harker's Journal.

24 October.—A whole week of waiting. Daily telegrams to Godalming, but only the same story: "Not yet reported." Mina's morning and evening hypnotic answer is unvaried: lapping waves, rushing water, and creaking masts.

Telegram, October 24th.

Rufus Smith, Lloyd's, London, to Lord Godalming, care of H. B. M. Vice-Consul, Varna.

"Czarina Catherine reported this morning from Dardanelles."

You wouldn't ever sit down and read as little as that of a book. But equally, that kind of chunk doesn't come across as slow-paced: it's just "today".

Other days its quite a lot, and you need to devote time to it, which again is not slow-paced. Indeed, you have to make sure you keep up!

To anyone other than OP interested in reading the book, I recommend Dracula Daily. To quote its website:

"Bram Stoker’s Dracula is an epistolary novel - it’s made up of letters, diaries, telegrams, newspaper clippings - and every part of it has a date. The whole story happens between May 3 and November 10. So: Dracula Daily will post a newsletter each day that something happens to the characters, in the same timeline that it happens to them.

Now you can read the book via email, in small digestible chunks - as it happens to the characters."

It's too late to start this year, but I think they do it every year.