Yes, when you tap Get Sample for a book in the iBookstore, iBooks will download an excerpt from the book to your bookshelf. You can read this sample and either purchase or download the complete book from the last page of the sample. Once you acquire the full book, the sample will be replaced in your bookshelf with the complete book.

The typical book is about 2 MB. Books that contain enhanced features such as audio or video will vary in size depending on the content. Enhanced books may take longer to download or require a Wi-Fi connection to purchase. The iBookstore offers textbooks that may be as large as 1-2 GB in file size and require a Wi-Fi connection if downloading from an iOS device. Download times for textbooks will vary depending on your internet connection. 

iBooks supports the industry-leading ePub digital book file type. You can sync freely available ePub files to iBooks using iTunes, or purchase or download books from the iBookstore. iBooks also supports PDFs, which can be manually synced to iBooks. In addition to ePub and PDFs, iBooks 2.0 and later also provides support for the new iBooks format used in iBooks Author. Other digital book file types are not supported at this time.

In certain countries you can browse and purchase Books from the iTunes Store on your computer. View this article for more information.

With Automatic Downloads enabled, you can automatically download new purchases to your other computers or devices. Learn more about Automatic Downloads in this article.

Yes, you can download ePub and PDF files on your Mac or PC. Add them to your iTunes library choosing File > Add to Library, or drag the ePub or PDF file to the Books library on your computer. To read these books, simply sync them to your device in the supported formats.

Yes, any books you've downloaded from the iBookstore will be automatically added to your iTunes library the next time you sync your device with your computer. To do this, your computer must be authorized with the same account that was used to download the books from the iBookstore. 

iTunes on your computer can show you the kind of book you have by selecting the book and then choosing File > Get Info. If the Kind is marked as Book, this is a book you downloaded from the Internet. If it is listed as Purchased Book, it is a DRM-free book downloaded from the iBookstore. If it is listed as Protected Book, it is a copy-protected book from the iBookstore.

Yes, you may download past purchases from the iBookstore at no additional cost. To download a book again, tap Store, then tap Purchased. Find the book you want to download again and tap the download button. You must be logged in to the iBookstore on your iOS device or iTunes Store on your computer using the Apple ID you originally used to purchase a book in order to download it again. View this article for more information about downloading past book purchases directly to your computer. Previous purchases may be unavailable if they are no longer on the iBookstore. Downloading previous purchases is not compatible with iPhone 4 (CDMA Model).

No, you cannot gift a book in the iBookstore at this time.

The number of books you can have in iBooks will vary depending on the amount of space available on your device. iBooks does not limit the number of books allowed on your bookshelf.