Google Books may be a good source for ebooks, but the browser window is definitely not the best interface to read them. It's uncomfortable, requires a lot of mouse scrolling and includes distracting elements such as links and ads. Luckily you can now use an alternative tool to read Google ebooks: it's called GooReader and lets you search, browse and read Google ebooks in a much nicer, more comfortable way.
GooReader reminds a me lot of iBooks, mainly due to its wooden bookshelf background and the way books are displayed - shaped as 'real' books, with covers and bookmarks. You can use GooReader to search Google Books by title, author or Google Book_ID. Results are shown on the bookshelf like real-life books, with color-coded bookmarks: green means you can read the whole book, yellow grants a partial preview and red means the book is not available to read.
To start reading a book in GooReader, just double click the cover. The book will open in separate window, with browsing controls at the bottom. You can maximize the screen, browse through pages (with a nice animation effect), access the book's table of contents and zoom in and out the text. Note that zooming in a lot may ruin text readability - depending on the quality of Google scans.
GooReader also includes the option to save books as PDF for offline reading, but this functionality is only available in the paid version. The app also lacks the option to add personal bookmarks and create lists with books, but with a bit of luck we'll be seeing these and other improvements in future versions.