The book stacks limit orders by price: bids below the last trade, offers above it. The top of the book is the current quote; everything behind it is the queue waiting to be filled if price comes their way.
Depth matters more than the quote. A book showing a thousand shares at the bid and fifty thousand two cents lower will behave very differently under a large sell order than one with even depth, even though both print the same spread.
Reading the book is harder than it looks. Much of the visible size is cancelled before it trades, and a large share of institutional volume never appears in it at all, resting in dark pools or being worked as hidden and iceberg orders.