Can I present in tablet mode?

If I understood your question correctly, then my short answer would be: "No! This is NOT possible".

My longer answer would be: "You may do this kind of projection but only if you have a reliable connection with a Microsoft Wireless Display Adapter (or something similar, if any)".

Explanation:

The problem with the Surface Book in your case is that, once you disconnect/deattach the "tablet-part" of the Surface Book (i.e., the touch screen) from the keyboard-part of the same device, you will have "NO PHYSICAL WAY" to connect to any ports such as HDMI or VGA.

For example, if you intend to use the mini display port connector to project your powerpoint presentation on a projector, you'll not be able to plug your "tablet part" to the "projector" because the mini display port is only available in the keyboard part of the Surface Book (the part that you just detached, so you cannot use).

In such cases, you may need to use Microsoft's Wireless Display Adapter (see https://www.microsoft.com/accessories/en-us/products/adapters/wireless-display-adapter-2/p3q-00001), which is a piece of hardware that casts the display on any monitor or TV that has an HDMI and USB ports (using Miracast technology via WiFi, where the HDMI is used for the display, and the USB for the power).

N.B. I tested this myself using the touch screen of my Surface Book and my Samsung TV.

I was able to connect the tablet part of my Surface Book to my Wireless Adapter (without any need to have the keyboard part attached), and displayed a powerpoint presentation on my TV while walking in my living room ;)

Please mark as "answer" if it is :) 

Best,

Ahmed.

If your projector supports Wifi-Direct or Miracast..

Sure you can do it!

The Surface Hub for example works really well with it... You can project meters aware from to it... I tested it... I was about 30 meters away and it is still working.

would like to use tablet mode

I think you may be confusing two meanings of "tablet mode".  In Windows 10 you cannot have multiple displays and use its tablet mode.  However (as I understand it) your Surface Book can be used without its keyboard, so if that is what you mean by "tablet mode", I think you could use it with a second screen but not with Windows 10's tablet mode. 

BTW notice that W10 now has a thing called Touch Pad button in the Taskbar.  So, I imagine that you could use that on your tablet screen to move a pointer on the second screen, without having a keyboard attached.  Otherwise, there is a way to use your tablet screen's touch screen as a means of controlling stuff on the other screen but it is pretty ugly and you have to be both skilled and lucky to be able to do anything useful that way.

Edit:  I just realized that there is also Project Duplicate which would allow you to use your tablet's touch screen and see what you were doing but depending on the resolution of the projector and the orientation of the tablet that might not look very good.  In any case, I think there are definitely ways that you could show stuff on a projector and control it with only your tablet's touch screen but I would recommend a trial before the show.   ; )

HTH

Robert Aldwinckle