Reading the PDF version on anything smaller than a tablet is difficult because it displays book-sized pages reduced to fit on the screen.
The preferred method is for you to get a copy of the PDF file onto your computer and read that copy at your leisure. The following instructions create that file via a two-PDF-reader procedure. You can stop when you see the book and read as you desire, or return back here, but the final result of the procedure is a copy of the PDF on your computer. You must have the Adobe Reader (free to download from Adobe), or a another reader with similar functionality, on your computer.
When you click on the button (at the bottom) the PDF is displayed using a limited online viewer. These can vary greatly, so be flexible when trying to do anything other than just read. Look in the upper-right of the screen to see a down arrow over a bar, which a mouse-over identifies as 'Download'. Click on the arrow to see a popup window where you click "Open" and select "Adobe Reader (default)" in the box next to the option. ***If this doesn't happen, or you are asked if you want to download it again, your PDF reader is too limited and this is as far as you can go. Cancel and Close the unwanted options and get back to where you can read it.*** Make sure the Open button is dark. Click "OK" and a new computer/system window for your Adobe Reader is generated, which displays the book. You can see full functionality of this reader by clicking on a Table of Contents heading and see the display jump to that location in the book. To make a copy of the PDF on your computer, click on upper left: File > Save as... > PDF... and see the "Save As" popup window. At the top, in the "Save in:" box, use the down-triangle to browse to a folder where you want the PDF stored on your computer, and save it.
This browser remains where you left it, so return from the PDF display back to here as desired - perhaps to find a different way to read the book.
Start reading the PDF, which is also the start the above procedure. You should not need to have a Google account to read it (it's stored on Google Drive as public) but I have seen some sort of Google pop-ups displayed when testing. I think I just pressed enter without typing anything and it progressed. The pop-up didn't show when I tried it again (I hate that), so I couldn't verify the behavior. Good luck...
FYI - to do it yourself, it's at: https://drive.google.com/open?id=0ByEg_dfRVu2bVFQ4RU1CeUxFaXc