Pre-ordering a print book does not grant you access to the corresponding eBook, however, you should be able to upgrade to the early release eBook for $4.99.
The details of the $4.99 eBook upgrade can be found here:
If you end up registering the pre-order book there (it happens automatically if you purchase it directly from oreilly.com) and the upgrade button is missing, let me know at firstname.lastname@example.org and I can assist you with that.
If you have any further questions,
You can contact us at:
1-707-827-7019 (Outside the USA)
7:30 am to 5:00 PST
Customer Service Rep,