Quote 1
"There are a good many books, are there not, my boy?" said Mr. Brownlow. […]
"A great number, sir," replied Oliver; "I never saw so many."
"You shall read them if you behave well," said the old gentleman kindly; "and you will like that, better than looking at the outsides,– that is, in some cases, because there are books of which the backs and covers are by far the best parts."
"I suppose they are those heavy ones, sir," said Oliver[…]
[…] Oliver considered a little while, and at last said he should think it would be much better thing to be a bookseller. (14.13-20)
Whenever a novelist starts talking about books, and writing books, and reading books, it’s time to pay attention, because he’s really just talking about himself. What are the books Mr. Brownlow is referring to, here, when he says that some books might look nice, but actually suck? Is he talking about bad novels in general (there were plenty of them then, just like now)? He might be.
Another possibility is that Dickens is trying to suggest that his own book (Oliver Twist) is better than the other Newgate novels that it was being compared to. In any case, we’re reading a book right now – Dickens was in the middle of writing it. Surely Oliver Twist won’t fall into the category of the books "of which the backs and covers are by far the best parts"?
The last part of the passage, when Oliver says that he’d rather be a bookseller than an author, is a deliberate jab at Mr. Bentley, the publisher of Oliver Twist (see the "Intro" section again). Dickens wasn’t making much money off of the book, and Bentley was making money hand over fist. Eventually Dickens wised up and started his own magazines so that he’d be the one making the money, but that wasn’t not until later.
Quote 2
Mr. Bumble […] after a few moments’ reflection, commenced his story.
It would be tedious if given in the beadle’s words, occupying as it did some twenty minutes in the telling; but the sum and substance of it was, that Oliver was a foundling […] who had terminated his brief career in the place of his birth, by making a sanguinary and cowardly attack on an unoffending lad, and then running away in the night-time from his master’s house. (17.82-3)
Here’s yet another instance of someone else getting to tell Oliver’s story for him – and it’s an awfully complete version, if not an altogether accurate one. Oliver didn’t have a chance to tell Brownlow his story before Mr. Grimwig arrived, so Mr. Bumble’s doing it for him. The story of Oliver Twist seems to be a story that just has to be told – everyone’s interested in it (including us), and Brownlow’s even willing to pay good money for it (as are we all, unless you’re reading it online).