When I started reading English books years ago, I tried both - looking up every word and reading the paragraph first and then looking up words. Both stopped me from reading much, I did not enjoy the book anymore and in the end I stopped after some pages. After that I didn´t try for a while. When I started my next book (btw. it was "Message in a Bottle" by Nicholas Sparks) I did not stop to look up words as long as I felt that I got the general meaning out of the story. It kept me entertained and it was the first book, which I finished. Years later I understood, what they were actually doing when "scuba diving" - the picture I had in mind while reading the book was "driving a water scooter" - it did not change the story. 

I think that I learnt more words by reading the complete book (and then still was motivated to start the next) without looking up some stuff (which I then might have misinterpreted) - than by working through some chapters intensely. 

Now with very basic Spanish (a lower level than my English was, when I started reading books) I try to read "side-by-side" (either buy both the English/German and the Spanish book - or a bilingual-book) and again I try not to stop to often to look up specific words. 

I also buy a magazine for Spanish learners, which has shorter, not to difficult articles and those I not only read but work through, until I understand all words and meanings (mark all unknown words while reading, then look up the words, read the text again). But as those texts are not that long, it doesn´t take to long to get to that point. 

When my language level is low, I look up every single unknown word for 2-3 chapters. Probably up to 80%. Especially in e-books, where it's really easy to look up the word with a simple tap. 

From the 3rd chapter or so, more and more words start sounding familiar because they get repeated. The further I read, the more words I memorize. 

If by chapter 5 I'm still looking up more than 5 words in a paragraph, it means the book is too advanced for me and I pick another book.

For reading books in my target language, I read them all on my Kindle instead of getting paper books.  If you can afford the $50 for a Kindle Fire, it makes it so simple to read in  your target language, because looking up words is so easy-- just put the cursor on the word and you have the definition.  (Kindle´s come with a default dictionary in English which would be what you would want anyway, but that can be changed to a translation dictionary in any language).

What I did when I was first learning Spanish was just get the ¨Kindle Unlimited¨ plan, which allows you to read any of a few thousand books, reading up to 10 at a time.  When I was A1, I was able to read many A1 level books for $9.95 per month, and then I started reading regular books for adults.  If they were a bit hard, I just turned that one back in and got another one. However, they usually are not hard even if I have to look up several words on each page.  

A nice thing about reading ebooks from Amazon is that virtually all of them have a free sample, usually the first chapter, so even if you do not get an unlimited plan, you can read a sample to see if the writing style and reading level is comfortable for you.

There are very many free books for the Kindle, as well as many that only cost a dollar or two. 

I was curious so I just started reading the sample of Cloud Atlas.  It is written in an old-fashioned style that I also found tedious.  Even if you do not get a Kindle, if you can get an Amazon account, it is helpful to read a free sample on their ¨Cloud Reader¨ before you buy a book.  Amazon staff informed me that normally you need a credit card to get an Amazon account, but a gift card can be used instead if you do not have a credit card.