I really like the Bible Timeline tool where you can see on a timeline what happened in history alongside biblical history, when biblical books were written, and so forth. What I'm usually scouring for in commentary introductions on one timeline.
Look at the most interesting and helpful features in Logos 5 here.
Resources -- There are many great resources available for Logos. The first four I searched for are Grudem's Systematic, IVP Essential Reference Library, Tyndale commentaries set, and the New International Dictionary of Old Testament Theology & Exegesis. All there. But Logos isn't just books converted to digital. You can also get resources like Tim Keller's library of sermons to search through. That's pretty amazing.
Bible Reading -- I've just started a Bible reading plan through Logos - 21 Days on Faith. Logos is one of the most complex and complete ways to study the Bible, as well as a way to read the Bible devotionally. There are adjustments than can be made to plans, they can be made into group plans, etc.
Important Questions & Concerns About Logos...
What's the Cost? -- I encourage you to look over the Logos 5 Base Packages. Logos as a whole isn't cheap and buying digital resources isn't like buying Kindle books, where you almost always can spend a few dollars less (sometimes far less) for a digital book. Not the same for individual books on Logos. The paper and Kindle copies of Grudem's Systematic are both under $30 and Logos lists for $40. Yet I've seen some sets that are significantly cheaper to get as a whole on Logos (49 Tyndale commentaries for $225). The question is really how you will use these resources and what makes the best use of them.
I thought about Logos like I thought about most Bible study software, that I'm paying for the ability to study the texts, original languages, etc. It's much more than that and the costs I believe are worth it. I'll say more about that in a little bit.
Let me add that Logos gives away a book every month and regularly has other giveaways. I just entered one today. There's also community pricing, pre-pub specials, and more.
Logos is Slow? -- I've seen people say (and at times felt myself) that Logos is slow. And to be sure...upgrades, downloads, and indexing take some time. But every moment of "slow" is speeding up something else. You get to search those books and have more resources to use in less time than it takes to look up each paper book. Those things that take time are necessary to create one place to conduct one search and have every resource listed. You can always pause indexing and such for a time when it works better for you. The tradeoff is one of the best tools you could have for Bible study. I'll take that tradeoff.
Paper vs Screen? -- I'm a huge fan of paper books. I'm also a big (and growing) fan of iPad and Kindle for books. While I don't ever see me replacing paper books completely, the helpfulness of being able to search a library is too good to pass up. Sure if I want to read a book from start to finish I'll often get paper or Kindle. But I can already see doing the majority of any prep work for teaching on Logos and the need to begin adding collections to my base package of resources.
I have a big personal library with many physical resources for sermon prep and Bible study and I just can't search through every book I'd like to for every sermon. I can see replacing large sections of my library with Logos. It makes each resources much more useful.
Logos vs Other Digital Books? -- The crucial difference between Logos and other searchable, digital formats is that Logos indexes your books for one big search of your whole library. This is why a Logos book is worth more. You will use books more and at times you may not consider its usefulness because searches will find things you will never think of looking up in a number of your resources. It's hard to explain the full value of this.
Let me put it this way: Every book you own (paper, Kindle) is searchable by you. Paper using an index, table of contents, looking up highlights, or oven using a filing system by which you record helpful passages by topic. With Kindle you can search for words. But with Logos its one search through every resource at once, do more complex searches, etc. It's not even comparable as far as ease of use, time consumption, or getting best use of a resource. With my 2,400 volume library I essentially have 2,400 books I can search individually. Now imagine one search through 500 or 1,000 of the most key resources with one results list. I can imagine it, and I want it. I've only gotten started.
Conclusion -- I'm a big fan of what Logos is doing and what it can do as I continue to add resources. I encourage you to look deeper at Logos. Compare cost to things like time, fuller usefulness of resources, and similar judgments and I think it's well worth the money. I love paper books too, and how they feel in my hands and how they smell. But what I like best about books is the content and Logos makes the most of it. See more at Logos.com.