Per the Turbine site at this link:
Clicky Question/Topic
How do I download the The Lord of the Rings Online: Shadows of Angmar client digitally?
Answer/Article
This download is a low resolution version of the retail copy of The Lord of the Rings Online: Shadows of Angmar created for people who have a 10-Day Buddy Key or do not have a DVD-ROM drive available. Before you begin downloading The Lord of the Rings Online: Shadows of Angmar, please make sure that you meet the Minimum System Requirements.
Minimum System Requirements
OS: Windows® XP
Processor: Intel Pentium® 4 1.8 GHz or equivalent
RAM: 512 MB
Video: 64 MB NVIDIA® GeForce® 3 or ATI® Radeon® 8500
Disk Space: 7 GB available
DirectX: DirectX® 9.0c
Optical Drive: 2x DVD-ROM
Internet: 56kbps Modem
Recommended System Requirements
OS: Windows® XP / Vista
Processor: Intel Pentium® 4 2.8 GHz or equivalent
RAM: 1 GB Video: 128 MB NVIDIA® GeForce® FX 6800
Disk Space: 10 GB available
DirectX: DirectX® 9.0c
Optical Drive: 2x DVD-ROM
Internet: Broadband DSL/Cable
Note: If you are running below 512MB of memory, you will need to run in Low or Very Low graphics or you will experience a lot of memory thrashing.
Additionally: If you are running below any of these requirements you may encounter graphical issues or poor overall performance.
So it is 5.5Gb but it's only the low res textures with the downloaded version. The initial download is a small 1.26Mb file that activates the Turbine launcher it looks like.