Please recommend a top-notch bookshlef speaker

It would be difficult to beat a pair of VonSchweikert VR1 monitors. Check out the review in Stereo Times online.

I second the VR1. I have had a pair since Sept and couldn't be happier. Good bass down to 50 HZ or so, small rear port allows placement in almost any place, and such a sweet, smooth and non fatiguing midrange. The design allows a wide range of listening positions. Deep and wide soundstage, speakers disappear. Great crossover. I have mine on a bookshelf and they are not boomy. Wife loves em! Beautiful fit/finish, great cabinets. Look great without the grills (and generally sound better without). They are very efficient at 89 db and 8 ohms easy to drive. Sound good with any type of music--pop, rock, jazz especially. I am listening to Diana Krall and she is filling the room. I run a 100 wpc Forte 5 and and adcom gfp750 in passive mode. Rotel 971 HDCD for source. Wireworld Atlantis II. ICs are Kimber Silver Streak WBT. I don't run a sub but they would sound really full if you did. You can find a used pair for around 600-700. Negatives: discontinued, and can't bi-wire/bi-amp. They are a bit deep on the shelf, but they work on my 10" deep builtins.

If you have power, a pair of NHT classic 3 might be nice too. They are sealed but really crave current. You'll get more dynamic range out of these guys. I have a pair in my HT setup. I still think the VR1 is more musical. If I could do it all over again I'd get VR1s all around in my 5.1 setup.

Be careful placing things on shelves in cabinets - it will collapse soundstage unless it is done very carefully and quite deliberately (a construction project).