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Good is relative of course. Given the layout of the backseat, the wife and I tried two options in the backseat (other than ones lap)
Lapdesk:
LapGear Home Office Lap Desk with Device Ledge, Mouse Pad, and Phone Holder (Sorry about the formatting)
and the Avantree Neeto.
We both agreed this lapdesk worked better as it rested on our legs by design, had good spacing and enough area for our gear in the backseat. The wife used this while vehicle was in motion across a five hour drive. We were on NC mountain roads back to our home, and it was better (of course) on straighter, flat roads.
The Avantree works, but in the backseat, it will rest mostly on your knees, and the legs offer almost nothing since they sit mostly or totally off the bench seat. The working space is slightly smaller than the lap gear. Depends on what you need on your desk after the laptop.