Don’t Make Me Think, Revisited a common Sense Approach to Web Usability Steve Krug

You actually can be too rich or too thin
...but computers can never be too fast. Particularly on mobile devices, speed
just makes everything feel better. Slow performance equals frustration for
users and loss of goodwill for publishers.
For instance, I prize the breaking news alerts from the AP (Associated Press)
mobile app. They’re always the first hint I get of major news stories.

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Unfortunately for AP, though, whenever I tap on one of their alerts, the app
insists on loading a huge chunk of photos for all the other current top stories
before showing me any details about the alert.
As a result, I’ve formed a new habit: When an AP alert arrives, I
immediately open 
the New York Times
site or Google News to see if they’ve
picked up the story yet.
We’re all used to very fast connections nowadays, but we have to remember
that mobile download speeds are unreliable. If people are at home or sitting
at Starbucks, download speeds are probably good, but once they leave the
comfort of Wi-Fi and revert to 4G or 3G or worse, performance can vary
widely.
Be careful that your responsive design solutions aren’t loading up pages with
huge amounts of code and images that are larger than necessary for the
user’s screen.

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Mobile apps, usability attributes of
You may remember that way back on 
page 9
I mentioned that I’d talk later
about attributes that some people include in their definitions of usability:
useful, learnable, memorable, effective, efficient, desirable, and delightful.
Well, that time has arrived.
Personally, my focus has always been on the three that are central to my
definition of usability:
A person of average (or even below average) ability and experience
can figure out how to use the thing [i.e., it’s 
learnable]
to
accomplish something [
effective
] without it being more trouble than
it’s worth [
efficient
].
I don’t spend much time thinking about whether things are 
useful
because it
strikes me as more of a marketing question, something that should be
established before any project starts, using methods like interviews, focus
groups, and surveys. Whether something is 
desirable
seems like a marketing
question too, and I’ll have more to say about that in the final chapter.
For now let’s talk about 
delight
, 
learnability,
and 
memorability
and how they
apply to mobile apps.