If you care about cases and manuals, it's a crapshoot with SecondSpin. I know that others have had good experiences but I have not.
I ordered 5 games from them and four of them did not come in original cases. Three of the cases were cracked (including the one original case) to the point of being nigh unusable: they either would not hold the discs securely or snap shut properly. One case was so badly cracked that the insert and outer clear plastic had a 3-inch tear.
One game was missing its manual and another game had a manual with its cover missing.
Even after several long calls, customer service refused to allow exchange or reimbursement, claiming that guarantees were made only for the discs' playability.
If you only care about discs, I will note that all the games I received played just fine. Three were near-mint and two were noticeably scratched but worked.
I guess the quality of the cases shouldn't have surprised me, as I'd previously visited their used CD shop in Sherman Oaks and it is the dirtiest music store in all of Los Angeles county. I left that store looking like I'd been in the coal mines all day.