We have new driver and firmware updates for Surface Pro 4 and Surface Book devices.

Click the headings below to go to the specific location for your device on the Download Center. At the Download Center, click Details then click + More to see all available downloads for the device. For all devices you can follow the same deployment process that is used for Surface Pro 3 described at Surface TechCenter.
Source: http://blogs.technet.com/b/surface/a...k-devices.aspx

Direct Download:

SP4: microsoft.com/en-us/download/details.aspx?id=49498

SB: microsoft.com/en-us/download/details.aspx?id=49497