Both tasks of GIVING A TALK and WRITING A BOOK are acts attempting to transmit information for the benefit of the recipient. To do this, you must

1. Do research and organize facts

2. fit the information you wish to transmit in the time available. For giving a talk there is always a time limit which you must observe while for authoring a book one has more flexibility and wider boundaries.

However, an important point to observe if you wish to be successful is to remember that 

   3. you should always try to present the information from the audience-center viewpoint and NOT from the author-centered viewpoint which you have already done in point #1 above. You must make the material (i.e. the information).interesting for the audience in order to capture their attention. Audience-centered also means that taking into account the type of audiences you are trying to address - from average adults with no special knowledge to a technical audience in the profession. I quote here my favorite advice for transmitting information: You should be able to explain anything in any amount of time to anybody at the level they can understand. Following this dictum you shall undestand that giving a TALK/LECTURE is very different from authoring a BOOK. Even ignoring time and space constraints, the two are very different tasks - good tools/techniques in one do not give same result in the other. In fact, some excellent tools for one task can have opposite and deadly effect in the other.. 

       4. Let me give just an example of point #3 above. You often show a slide during a talk. Remember the purpose here is to improve understanding of the information being transmitted and NOT the amount

of information during a talk by letting the visual and the audio channel reinforcing the each other during the limited time constraint of a talk. A slide is NOT a tool for you to cram more information into a talk by using small prints and messy photo/figure. If not coordinated with you voice delivery they only serve to distract the audience from the audio portion of the your delivery ending up not helping understanding but only distraction harmful to your purpose of information transfer (see NOTE 1 below)

        5. Similarly it is often inappropriate and often deadly to read from a script for a talk. A script is more like a book. Reading from a script should be avoided when giving a talk. A talk should be more like a conversation between two people in which one side do both the Q&A 90% of the time. This is why during some lectures the speaker often encourage actual questions during or after the lecture. .(however, see note 2 below)

        6. Every speaker or author wants to be successful. But one often mix up tool/techniques for these two  differnt tasks with the same purposes and ending up with unintended bad consequences fiting the idiom "the road to hell is paved with good intentions".

NOTE 1. Which is why even in book or published papers., Appendices are often used so as not to distract the process of information trnasfer. 

NOTE 2. A political or public relation speech serves different purpose than  giving a talk.even though they have some commonalities of information transfer. Teleprompters are used to avoid mistakes since often the speaker did not author the speech him/herself