sudo apt-get install emacs25

~ sudo add-apt-repository ppa:kelleyk/emacs

~ sudo apt-get update

➜  ~ sudo apt-get install emacs25
[sudo] password for psn: 
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following additional packages will be installed:
  emacs25-common
The following NEW packages will be installed:
  emacs25 emacs25-common
0 upgraded, 2 newly installed, 0 to remove and 0 not upgraded.
Need to get 21.0 MB of archives.
After this operation, 90.8 MB of additional disk space will be used.
Do you want to continue? [Y/n] y
Get:1 http://ppa.launchpad.net/kelleyk/emacs/ubuntu xenial/main amd64 emacs25-common all 25.3~1.gite0284ab-kk1+16.04 [17.2 MB]
Get:2 http://ppa.launchpad.net/kelleyk/emacs/ubuntu xenial/main amd64 emacs25 amd64 25.3~1.gite0284ab-kk1+16.04 [3,792 kB]                                                                   
Fetched 21.0 MB in 1min 16s (276 kB/s)                                                                                                                                                       
Selecting previously unselected package emacs25-common.
(Reading database ... 153708 files and directories currently installed.)
Preparing to unpack .../emacs25-common_25.3~1.gite0284ab-kk1+16.04_all.deb ...
Unpacking emacs25-common (25.3~1.gite0284ab-kk1+16.04) ...
Selecting previously unselected package emacs25.
Preparing to unpack .../emacs25_25.3~1.gite0284ab-kk1+16.04_amd64.deb ...
Unpacking emacs25 (25.3~1.gite0284ab-kk1+16.04) ...
Processing triggers for mime-support (3.59ubuntu1) ...
Processing triggers for hicolor-icon-theme (0.15-0ubuntu1) ...
Processing triggers for man-db (2.7.5-1) ...
Processing triggers for install-info (6.1.0.dfsg.1-5) ...
Setting up emacs25-common (25.3~1.gite0284ab-kk1+16.04) ...
Setting up emacs25 (25.3~1.gite0284ab-kk1+16.04) ...
update-alternatives: using /usr/bin/emacs-25.325 to provide /usr/bin/emacs-25.3 (emacs-25.3) in auto mode

~ emacs25