When the Nexus 9 was first released we were without a custom recovery. Normally recoveries come out pretty quickly on devices with unlockable bootloaders. Even if Team Win doesn't officially release a recovery automatically we still normally see an unofficial recovery come out almost the same day from other developers. DeesTroy and the Team Win team have been hard at work since the device came out. They even started work prior to receiving the tablet. They have finally released TWRP for the Nexus 9! For now it looks like the theme is set for the same size as the Nexus 7 which means that the theme is a bit undersized. Im sure someone will release a theme to correct the size soon. Other than that this version of TWRP is fully functional. If you are already rooted you can install TWRP with the TWRP manager app. Head to the link below for the download.
Via Play Store