Hypermedia API Link Traversal & Practicality

Hypermedia API Link Traversal & Practicality

I've been trying to build a hypermedia based API. Things seem working
well. Say when I fetch /books/isbn/12313441213 I get something like this:
<book>
<id>123</id>
<name>Hypermedia APIs</name>
<description>Basic api design techniques</description>
<tags>
<tag>rest</tag>
<tag>api</tag>
<tag>service</tag>
</tags>
<authors>
<link rel="author" uri="/authors/id/22" />
<link rel="author" uri="/authors/id/18" />
</authors>
</book>
Now I can traverse the authors from this resource. When I fetch
/books/by/author/id/18 I get something like this:
<books>
<book id="123">
<name>Hypermedia APIs</name>
<link rel="self" uri="/books/id/123" />
</book>
<book id="191">
<name>Chef Recipes for Rails Developers</name>
<link rel="self" uri="/books/id/191" />
</book>
<book id="220">
<name>Rails 4 Cookbook</name>
<link rel="self" uri="/books/id/220" />
</book>
<book id="292">
<name>Ruby 102</name>
<link rel="self" uri="/books/id/292" />
</book>
<book id="432">
<name>Semantic Architecture</name>
<link rel="self" uri="/books/id/432" />
</book>
<book id="501">
<name>Service Oriented Design</name>
<link rel="self" uri="/books/id/501" />
</book>
</books>
Which also seems to be working fine for me. Whether or not this way of uri
templating is good, my question is around how practical to traverse links
like this?
Considering you want the resource in full-depth (including author
details), you have to make at least 3 calls to the server. Again for the
collection, you have to make tons of calls to the server. Yes maybe I
could utilize resource expansion here, but then why would I use hypermedia
links at all since all of my clients will be using expanded resources in
time.
I understand we are gaining lots by letting clients to traverse links (ie.
if clients build relation based resource discovery, they will be impacted
minimum when we change the api, or they are forced to get the most recent
schema from the resource endpoint itself, etc). Then again, practicality
of this approach, or the performance of this approach would kill the
system.
Either I'm not getting something in hypermedia api design, or hypermedia
api sounds great but it seems it's just a theoretical idea, not a
practical one.
Any thoughts on this?